Overwintering goldfish in Manitoba

[SmallFry]

Hi, I'm posting this question on behalf of a friend who is looking at taking some fish her father in law is no longer able to look after.

She has no space in her smaller home for a tank large enough to over winter indoors, and was wondering if they could survive outdoors through a Manitoba winter..
We'd thought we could use an air pump to keep things oxygenated and perhaps even a cattle trough heater to keep things from totally freezing up. She will also be building a pond for them, so we could probably insulate the sides of that too..

Does anyone do this, or are we just plain nuts?

Thanks in advance,
Rob