Normally a number of bikes can go through on one pass. The leader needs to be carrying the pass and they all need to stay together.this Canada pass site says $136.40 for a family/group annual pass and also says they must be a single vehicle.???
http://www.pc.gc.ca/pn-np/ab/banff/visit/tarifs-fees_e.asp?park=1
I am not sure of how many can go through but I frequently do it with 4 bikes.