As I indicated, I cannot provide specific legal advice in this forum, rather only answer to general aspects of law.
Incorporating by reference other documents DOES NOT MEAN THOSE INCORPORATED DOCUMENT BECOME UNCHANGEABLE.
When a contract incorporates another document by reference, generally it is the incorporated document as it exists at the time of the original contract became effective, unless the language of incorporation includes provision for future changes in the other document being incorporated.
For example: A makes contract with B, but the contract incorporates by reference another contract involving parties B and C. The contract incorporated is the one that existed at the time the A-B contract was formed. But contracts are freely changeable so long as both parties agree, so later if B & C change their contract, and the change is such that it impacts the overarching A-B contract, that change in B-C contract won't be part of the A-B contract: even though the B-C contract was incorporated into the A-B contract, it remains independent with respect to itself, and therefore fully changeable.
It is the original A-B contract that needs to account for the terms in incorporated documents, whether to "freeze" the terms incorporated as of contract formation, or allow for future changes in incorporated documents.
e.g. "...this A-B contract incorporates by reference the B-C contract, including all future modifications," or similar.
If a contract incorporates other documents likely to change, then the contracting parties need to consider carefully with respect to incorporation of other documents precisely for this reason: otherwise, the duties of parties could be changing frequently, and not all parties may be aware of those changes.
Be aware that collective bargaining agreement are incredibly detailed and complex "fine print" documents compiled among many lawyers on both sides -- in most case hundreds of pages -- so there may be provision accommodating future changes to incorporated documents elsewhere in the CBA, and it may be in an entirely unrelated section!
Because of their scope -- encompassing hundreds of employers and thousands of members across states -- CBAs generally allow for great flexibility and changes, such as those reference in the original set of circumstances described.
Lawsuits involving CBA often take years to wind through the system, and courts almost always first try and have the parties resolve the problem among themselves, precidely because of the complexities involved.
I hope this helps with a bit more perspective, and again, I'm sorry I cannot provide specific legal advice on the legal agreements referenced.
For advice on those documents, they themselves have to be reviewed in their entirety, exactly because conditions and clause often get placed -- intentionally or inadvertently -- in different, possibly unrelated, sections.