I run a pro studio. A small pro studio, but pro none the less. Plugins have absolutely gotten to the point that they're worth substitutes for outboard gear, but that doesn't matter much when you're tracking. If you showed up at my studio with a giant rack full of gear to run your bass through I'd happily use it, unless of course it didn't sound appropriate for the session, in which case we'd switch to any of my pieces of gear that delivered the desired result. Maybe a combination of yours and mine. Whatever gets it done it what we'd use. Some studio owners will only use their gear. Other studio owners don't have much invested in nice gear for tracking and may require the players to bring their own gear in to supplement the studio's.
The answer is "it depends." As to the statement that "...you were expected to bring along a rack with a tube compressor and some kind of tube mic preamp. Of course, the more vintagey the better..." I would say that is nonsense, especially when you get that specific. The engineer might not want you to track through a compressor, or the player might not want to use one during tracking, or they might prefer something like an 1176 or a Distressor both of which do not contain a tube, or they might want to track through a 1073 which has no tubes, or they might bring in an ART Tube MP which does have a tube but in my experience brings nothing sonically to the table... So again, it all depends.