Well, certainly they'd give required documentation and design for specific contracts.
Whatever they do provide may not be sufficient for ground-up design and, if it is, it's most certainly sequestered (proprietary, authorized for specific contractual use only) from the ground-up engineers at Tamron.
Of course, you can often creatively work around such contracts. For example:
1. Use the information to build a testing rig for the Canon lenses that tests every single command, with emphasis on edge cases. This is needed for the contract anyway.
2. Use the test rig to validate a "lens" that behaves according to the reverse-engineered spec. Tweak until it passes. At that point, if your test rig is complete, so is your reverse-engineered specification document.
Even then, though, they may be using a procedure developed for say a Canon 18-55 to acceptance test their own design for a 150-600, which may not be appropriate.
Also, it depends on how a contract is written (and how faithful the company is to the contract). If I were a Canon lawyer, I would specifically preclude any sharing of Canon intellectual property and associated technology across the company. If I get a proprietary spec from a client, I can't copy it longhand into my notebook and then use it for other purposes, nor can I embed it in software and use it for other purposes (at least not legally).
Whatever the case, the third party glass designers aren't privy to the information required to match Canon's own designs and algorithms, for obvious reasons.