Huh. Turns out M*A*S*H airs on History Canada in HD. Season 1 finishes syndication today. Might start PVRing the episodes to cap them once I get a good card.
Nope. It's in the original 4:3 frame. I haven't been the DVDs so I don't know if the DVDs are just really good or the HD feed is a proper good upscale/re scan. I'll see if I can get an example to compare it with.