I actually work in a union shop (as a SCCM Admin) - the irony is that during the migration from SCCM 2007 to 2012 they sent me to training, and one of the guys who was there as well was Carnival's SCCM admin - he described a rather unique and complex environment. I can't a imagine a bunch of consultants - even with training taking that over - plus I've never met a consultant who knew anything about the dark arts of client management (I know they exist obviously but they are rare flowers).
Anyhow union jobs don't necessarily guarantee better wages etc (that said - I've always got 5-7% year after year, where some of my colleagues have got nothing), but they do offer collective bargaining and an actual contract that defines the terms of employment, and severance - if the company were all of the sudden wanting to outsource everything. There's nothing in the cards that would force us to train our replacements - and not get a check.
In other-words - you're no long at will - you have a contact, and if they don't uphold that - you (or your union) can do something about it. In years prior to this - I never had a contract as it were - and my employers could fire me under the same guises that Carnival is. Worth mentioning too - these CEO's don't start work without well defined contacts, but so many of us have and are.