I've been ostercized....for supporting something I believe in...?

CYA is hugely important (Cover Your A$$). Whenever one of them does something that negatively impacts your work (withholding info, being uncooperative) you need to send them a detailed e-mail noting what you need and by when. Make sure to CC your boss on everything. They can then choose to do their job and give you the info/help or they can go on the record refusing to do their job. Either they'll start working with you again or you will have enough ammunition to force your boss to step in.