Thanks again.
Still confusing "you don't need anything but your own insurance if staying less than 180 days"...but..."you should have this card"...and it also says for "interprovincial" travel, which to me means going from BC to Alberta, etc.
Oh, remembered another one - up to NS, NB, PEI, in our us-plated rental car. This was in 1996.
I'll be on the safe side and get one next time I head north.