It's been awhile since I started this topic, but since others have been having the same issue, I wanted to share an "ah-ha" moment I had. I'm away from my Mac right now so I can't confirm 100% that this was my issue in every case, but what I noticed was:
When I had this problem (controls for MBL not showing up) I would try to click that checkbox on and off to no avail. Like someone else posted, this even happened outside of multicam. What I needed to do was click on the area where the name of the effect was (next to the checkbox) to make it "active", much like you'd click somewhere within the inspector, event broswer, timeline, etc. to make those areas active.
I can double check this, but I do know that when this happened to me after I originally started this thread, I would make sure the box was checked and then click on the name of the effect, and I haven't noticed any problems since then.
I hope that explanation was clear, and I can confirm later when I'm in front of my Mac.