In what way?
If you're talking about Manitoba taking the northwest... I mean, if Manitoba really wants trees, I'd say take 'em. Thunder Bay, the only populous city out there, is kind of orphaned as it is. The entire Kenora District (Albany on this map) could become an autonomous region and nobody would notice a change.
As for area codes - The Kenora District (more or less) is 807. The rest of Northern Ontario ("Ishpatina", named after a ridge that, doubling the height above sea level of neighbouring Sudbury, is the highest piece of land in Ontario) is 705. The Capital region is 613. The Kawartha region is 705, but with Peterborough and the surrounding area connected with the GTA via GO Transit - and the region on this map including the Great Lakes region - it will probably have its own area code soon. Southern Ontario, aside from the Greater Toronto Area, is 519.