That was going to be my next question. How are the chances of succes requesting a press pass? Does that cost you anything, and how likely are they to supply you with one if you're not actually a press photographer?
Also, do those press passes commonly come with (contractual) limitations on what you're allowed to do with your pictures?
I've only really worked professional cycling w/ a press pass so can only comment on that. The press pass itself is free, the question is what level of access do you get. In cycling - the pre-race venues (where the team busses, cars, etc line up) are open to the public to encourage fan interaction with the teams/riders. The riders usually come out, sign a few autographs, head to the start line to sign in for the stage, come back, hang out on the bus, then roll over for the start. Pretty much anyone can walk around that area and get photos.
The first level is a the press credential. You have to go to the press office and let them know who you are shooting for (team(s), publication(s), sponsor(s), etc.). The larger multi day races sometimes ask for a letter of asignment from the team/publication/sponsor if you're not a "regular" on the circuit. Sometimes they don't. Up in Canada when I shot a pro tour race (an international top level race) I had to also present credentials from a professional association (I'm a member of an international press writers/photographers association AIPS - and also the NSSA - the US version of the same association) to get my credential. It really varies between events. Most larger races have online signup where you can submit most/all of the above several weeks/months before the event and you'll get an email about a week or two before the event to let you know if you were approved or not.
The photo credential helps you get in behind the barriers before the start. It gets out inbetween the crowd and the sign in stage. At the finish, a photo credential will get you into the "photo area" near the finish. You'll just have a barrier between you and the course, you won't have to fight the crowds who have been waiting all day, but the placement of this area isn't always in the best photo spot for the finish.
The next level of access is also free - it is a "course vest" - it allows you out on the course itself, inside the barriers where allowed, etc - this is a bit harder to get as there are a fixed number that can be handed out - some are given for the week, others for the day, depending on the "assignment" length, etc. At the start, you can move around a bit more freely near the sign in table, etc. There isn't too much advantage at the start over just the photo credential. At the finish, this bears fruit. You can be on the road, beyond the finish line as the riders charge towards the line (if it is a pack finish) or as the rider on a mtn finish crosses the line. They tape out areas on the pavement at least 30 meters beyond the line - usually more - and varying by setup (narrow, etc). The photogs are held off the course till the course marshalls let you out, then all race to a spot in the taped out "pens" and you line up your shot.
The premium access in a pro cycing race is to get a ride on one of the photography motorcycles. This can have an associated fee per day ridden to help offset the cost of the organization having to hire, feed, and house these drivers for the week. These motorcycle drivers are "vetted" and work their way up to these larger races. They know where they are allowed to take you, are briefed on road hazards on the day's stage, and know when they have to clear the course for the finish and will then drop you off at the finish line. There are usually 7-10 of these in a multi day race, and of these (like the course vests) some (3-4 depending) will get a ride for the week, others are doled out a day at a time to those with course vests (they get a temp "moto" vest for the day) based on assignment and need. You get to use the moto as transport along the course and while you're the lowest priority on the road (riders, safety/docs/medical/neutral support/officials, team cars, etc... ) you can go ahead and scout scenics, let the peloton pass and then work back up through the pack (the moto can only go the direction of the race on the road, no back tracking), can pace the head of a pack or breakaway to get shots so long as you're not providing aerodynamic benefit to the riders, etc. Tis a sort of "you're the director" type control. Tho you risk getting caught behind the riders if the road narrows, or if they are descending a steep mountain, etc... it is all about knowing the race, the options, the situation, where specific riders are, who's winning overall, who's gunning for a single day victory, etc... Then, at the finish, there are usually a few spots set aside for the moto photogs as they couldn't wait at the finish all day to get their best spot...
As for restrictions - just those I mentioned in my earlier post in this thread (sorry - I'll save my fingers and won't bore you with a repeat... (chuckle)).
Folks can work the circuit for years to get a ride on a moto at all, let alone for a week. I'll admit it is the best seat in the house. Perhaps even better than sideline access at NFL - well, if you know how to position yourself to be where and when the decisive move is going to happen on any given stage... I've had days when I've "nailed it" and been at the right place all day and got shots that no other shooter got. Others I've gotten bubkis... just part of the territory.