Holding that "Rule 408 does not exclude evidence of alleged threats to retaliate for protected activity when the statements occurred during negotiations focused on the protected activity and the evidence serves to prove liability either for making, or later acting upon, the threats" because the evidence was not introduced in order to prove the validity of the grievance which served as the subject of the negotiations
Concluding that "[i]n this case, timing is everything," where "[t]he closing of the department comes on the heels of the union's organizational activity," including filing a petition for a representation election