Canadian personal income tax law re land sale by US citizens

US citizens/residents sell land in Canada and 20% is withheld. Are they allowed to file non-resident tax returns, report the actual gain and receive a refund?

Do Canada and Ontario taxes both apply?

Are the rules regarding cost basis related to gifts and inheritances the same as those in the U.S.?

TIA!

Don’t take my word for it, but I have always heard that if I moved to the US (not in the cards unless a good medicare law passes), then my pension would be subject to a flat 25% federal and no provincial tax. Maybe it is different with real estate and maybe it would be taxed at the capital gains rate.