Just in case this helps somebody, it took me some time to figure it all out. And I'm still not convinced I got it all correct, which should act as a disclaimer (go double check yourself before doing something like this).
I bought a motorcycle out of Quebec and was to meet the owner in Winnipeg so I could ride it home. I won't get into the story here except to say while crossing Alberta it was between six and eight degrees in the pelting rain...
I needed a:
"Binder of insurance" from ICBC which covered the bike while in transit. Get before you go.
A "Manual Temporary Registration" from any Manitoba Autopac agent which allows you to operate the vehicle on Canada's roads through reciprocal agreements between provinces. It's just a flimsy piece of paper you're supposed to tape to your "windshield". So bring plastic and some strong tape with you and try to figure out where to stick it.
All this allowed me to travel from Manitoba to my home. Then the temporary registration becomes invalid (but not the ICBC Binder apparently, see below).
Motorcycles are exempt from the mandatory "out of province" vehicle inspection but the ICBC agent still needs to physically see the vehicle to confirm the VIN.
So you need to go and get a permit from them to ride the bike, one way, to the ICBC agent. According to what I was told, insurance for the trip was still covered by the Binder. But the agent was pretty fuzzy on it. I'd double check that with ICBC proper.
They check the VIN and issue you a BC registration and whatever insurance/plates you desire. Pucker up and brace yourself for the HST, it hurts.
A copy of the transfer is given to you so you can send it back to the original owner, which allows them to "deregister" the vehicle in their province.
One thing for sure, on a trip like that you get to know your new bike really well, really quickly.
Hope it helps somebody, someday.