The issue here is whether by doing so the company just breached a perfectly viable and enforceable contract. If so, the state labor department may have a say and the union can possibly sue the company and file a motion to force the new company to be a party to the contract. The company may have to pay restitution or some form of equity damages for this possible blatant attempt to undermine the union agreement. You should speak to your union steward or the headquarters for the union and see if this something the union is going to pursue.