I've used a few rental cars recently which had what I assume was satellite radio. Was quite impressed until I did some research and it looks likes satallite radio is subscription only at approx $15 pm?

Never seen any digital radios in Canada. Are they not available here?

Is it just AM/FM then?

Satellite radio is indeed subscription only
As you may have noticed most channels are advert free and those satellites are kind of pricey

Yes they are Sirius satellite Radio.
You can buy subscription cards l got mine from the source l payed about 50 bucks for 3 months.

If you own a smart phone try Tune in Radio App, you can tune into any station from any country. Including Radio 1, 2, 3, 4, 5 ect Sky Sport News (My fav on a Sat morning) and Talk Sport. Same app works at home on a laptop or PC.

no digital radio at all...my mum brought her iPod dock which has a DAB build in, when she came on holiday and it never picked up any stations!

Yup satellite radio. Two brands, all run by the same company now, Sirius and XM. You can get the same station from mid-north Canada all the way down to southern Mexico and the Caribbean. Very popular with commuters and people who do a lot of driving. Not so much with people who are just in the house and can stream internet radio unless they have shows you particularly like. They also generally come as standard in most new cars these days as well.