Dr John Stockton wrote:

But one would not expect a world standard to apply in an American
system, and that's what Canada uses.

If I went to America, I'd almost certainly use my mobile if I needed to
call '911', but if I dialled 112 it would work.

If an American brought their tri/quad band GSM phone over here, and
dialled 911, they'd be connected.

So, besides going to a payphone or using a hotel phone (or whatever) it
doesn't really seem to be much a problem.

As for the original post comments, I'd always call 999 if there was
anything that was potentially dangerous and needed urgent attention.
That has been driving behind an obviously drunk driver (one who nearly
had a head-on, the other that did in fact go off the road and fly into
a ditch), seeing debris on the road, reporting a driver stopped in lane
3 of a motorway.

You aren't likely to be told off unless you're asking for advice on the
best exit to take to get to XYZ, or where the nearest McDonald's is!

I've got hands-free and wouldn't (and don't) hesistate to call - and I
hope that I've prevented at least one or two potentially fatal
incidents. Why leave it to someone else to call? The police and other
services are well used to multiple reports of the same incident, but
would prefer that over no reports.

Jonathan