I work at a hospital in Radiology and our corporate director makes it very clear that we are not to tell the other vendors what their price is. We have had other hospitals actually send the bids to other vendors now if it was on purpos or not I do not know, but it is definetly frowned apon.
I can't speak for certain, but in the land of Plant Operations and Facilities Maintenance, it is not against the rules.
Government facility, that is a different story.