I have worked with many electrical Contractors that have used BIM for the first time and it is very costly to get up to speed. Once their people are proficient and the Electricians follow the plan it seems to be very efficient and quite a bit less rework or moving of individual conduits.
Also your general contractor needs to draw the building and its structural components correctly or you will have just as many issues as without BIM.
One last thing that helps out efficiency is if All of the contractors on site use BIM and if anyone is out of the location they are supposed to be in they have to correct their mistake and if they impact the other trades they have to compensate that trade (The last part is a little hard to prove).
-Ed