I don't remember that the surveillance video said the vehicle was northbound on Trinity north of Book Road. Bullman was on the corner (well, one house east of the corner) of Book and Trinity; he would have mentioned if the vehicle turned onto Trinity Road. Instead he said it went west on Book Rd.
I'm familiar with the area, drive by it regularly, but can't think of any obvious "businesses" at that corner, but that doesn't mean there isn't one. Some neighbours have them (surveillance cameras) on their farm properties. There are several businesses farther north, as you approach Wilson Street. The Ancaster Fairgrounds are on one side, several other commercial places on the other.
So there is a discrepancy here. Either the surveillance video actually captures the two vehicles northbound on Trinity south of Book Road (but north of Butter Road, the next cross street), or Bullman was in error when he said he saw them heading west on Book Road towards Brantford. The latter seems improbable to me, because he was right near the corner and could certainly have seen whether they turned or not. Also, if you're up to something, best to keep to the darker, less well-lit roads. Book Road is like the dark side of the moon at night.
Or, perhaps they went west on Book and realized they were lost (but surely they have GPS?), turned around and came back, then north on Trinity to Wilson Street which would also take them west to Brantford, but the chances of someone seeing something untoward in their vehicle on the brightly lit road would be a deterrent, I think.
I missed that testimony about the surveillance video; the time stamp on it might suggest whether they went west on Book, changed their minds and came back. That doesn't sound logical to me, but we're not dealing with Professor Moriarty here.