Our title company charges a doc prep fee on HUD-1 line 1105. this if for prep of the preparation of this same Hud-1. under the new respa rules (3500.12) a lender cannot charge for doc prep of hud-1, so can we can we pass on this cost to the customer?

Under the old RESPA rule this was true as well.

Usually the doc prep fee is for other documents the title company has to prepare for the closing. So unless the fee specifically references TIL and/or HUD preparation I wouldn't waste a lot of time on the issue.