It should be noted that the bill won't be different from an insured person bill, the prices are "posted".
It sounds like it was the Canadian insurance provider who screwed them, though. They said[2] that since she had a bladder infection prior to getting the travel insurance, it was a pre-existing condition and therefore wasn't covered. So basically, if you get your travel insurance and come across the border, don't expect it to cover anything like a heart attack, an abcessed tooth, a prescription refill, etc.
[2]https://www.change.org/p/blue-cross-blue-shield-pay-for-jenn...
As someone who lived in Canada for 10 years, I can understand that. The blindness Canadians have to the severe problems in their own healthcare system is amazing. Take a look at the massive problems in autism care in Canada. Let me put it this way, it was cheaper (free), faster, and superior in every way in the US as opposed to Canada, where it was far more expensive, years in waiting times, and in the end got no autism assistance. To be fair, this was back in 2011 when we finally left, but having kept an eye on the system (what with having family there still), it hasn't really improved.
It happened to a friend of mine who was hiking in Canada a year or two ago. Her son cut a big gash in his foot and they couldn't get online, so I had to call around to find an emergency room they could go to. The local emergency room basically said in lieu of proof of (internationally-accepted) insurance they would need $800 up front if he wanted to be seen. I think they wrapped a towel around it and drove back to the US.