I've kept Pep shrimps with BTAs in the past with no issues.
A while ago, I tried to move my Haddoni ( carpet ) anemone to another tank. I ended up damaging it a bit, so I left it in that tank to heal. I thought it was completely healed, though it was moving around a lot. Since it was moving a lot it was easy to move, so I moved it do the downstairs tank. (( I was about to have knee surgery, and wanted to be able to keep an eye on it without having to go upstairs )). Got back home after 2 day, and noticed that that a couple spots on the outside rim were torn up a bit. That night I slept downstairs and noticed the Pep shrimp picking at it.
Ended up leaving a room light on for a couple of nights -- my shrimp only come out at night -- it give time for the anemone to heal. Now that is it healthy again they stay away from it.
So, what my long post is trying to say is that there may have been something wrong with the RBTA, that "allowed" the shrimp to attack it.