Once again interlog nails it:
The court case is going to decide whether the changes are contractual or not.
If they are not contractual, there is no need to change contracts.
If they are contractual, it is up to BA to decide to find the changes reasonable and issue a change to the terms of the contract with it then up to the employee to decide to accept or not.
It is worthy of note that the 90 day rule is for the dissenters to ponder their decision. If the notice of termination comes with the new contract, one can be back at work the following day clutching a newly signed contract.
Now that is food for thought