Well, think about it from an employer's side of things, you've got 55 odd sparkies on your payroll, who do work at a site you've got the contract for. All of a sudden (well not that suddenly in this case, actually), you lose that contract. If you don't have any other work for them to do, their positions are now redundant in your business, if you're still solvent you will need to provide proper redundancy packages for them.
Side note, doing the maths here, if the unions claims are true, that the new positions being offered are a 65% reduction in pay, that would mean even the lowest paying position @ $70k, would have been paid $200k under the old employer. If you're earning that much cash, you must either be pretty **** hot at your job, or have the best luck in the world. If you're really that **** hot, then you shouldn't have any issues finding a new job paying that much again.