I really think this is performance craft, not a practice room skill. I don't think learning to chase randomly fluctuating pulses is going to work. If you analyze what they're doing wrong, usually it's not totally random. They tend to screw up the same thing every time. I don't think it's a good practice to simply adjust to all of their timing errors. What if there's another good player on the gig? He's going to think you suck as much as they do.
You can try listening to them extremely closely, like you're playing free jazz, or trying to ignore them completely. I used to make it a game to see if I could force them/trick them into actually listening to me by what I played. There's also a difference between having metronomic time vs. actually communicating it to the other players, so I'm always thinking if I'm playing the right stuff the right way for this particular batch of knuckleheads.