I always take my own bass, if I take a cheapy then I'm happy to let someone else use it if I take something more precious to me then (unless I know the borrower well) no. I'd expect the PA and backline to be provided by the house/organiser.
As an aside I had a run in with a pillock a few months back at a local jam. I plugged into the bass amp and the aforementioned came up to me and said not to use that amp to which I was plugging in. I said sorry mate, didn't know it was damaged to which he replied, 'it isn't, it's mine'. After that I may have requested that he do one, but Personally I would only put backline on a Jamnight stage if I was happy with all using it ....albeit I might tape down the controls!