* Since I'll use Canadian ATC service during the overflight, will I
get a bill from NavCanada when I get home?

Yes, it's still around $15 (Canadian), and it's good for a whole quarter -
so if you fly back before the quarter is over, you won't get another bill.

When did this go into effect?
I have never been charged for previous overflights.
If I landed at a Canadian airfield, I was charged, and rightly so.
It is my understanding that there is a bilateral agreement not to charge
for overflights.