@alistair millington and @E
As has been repeatedly commented, the couple GAVE their address.
But to answer your question about giving addresses in Canada, let me give you my own personal experiences, which I admit are hardly representative:
I have had to call for 911 only twice in my life so far. The first time was from a landline, and the operator, who already knew where that phone was, verified the address by asking me to confirm it. The second time was by my 3G CDMA phone, where the operator asked me exactly where I was. I understand that dialling 911 on that model phone automatically switches on the GPS, though it's not clear if the 911 operator had access to that. In both cases, the operator verified the address/location, and emergency services were there within 5 minutes.
It seems to me verifying the location of the caller is, or SHOULD BE, SOP. This is my experience, and it seems to be the experience of E, that other Canadian. It should make zero difference if I'm using a land line, mobile, VOC, VOIP or two tin cans with a string.
Arguably there are situations where you cannot get the caller to verify the address, in which case, then, yes, VOIP is a disadvantage. But even then, as E pointed out, if the e-commerce websites seem to know where I live (heck, even the very El Reg page I'm looking at right now has ads that seem to know which region of Canada I live in, and I never told them that), then there must be some way to verify the caller's location beyond the DB.
But this isn't one of those cases.
@E: From your comments, my suspicion of what kind of 911 call centre ComWave had is only strengthened: Not highly trained professionals, but outsourced, minor league ones.