You said you "believe" and "think" that Ottawa gets Detroit on cable. Are you now saying it positively does?
Yes, Ottawa positively gets Detroit on cable these days. It's been at least a decade since the old microwave system that received Rochester's big 3 from a site near Belleville and fed it up to Ottawa was decommissioned.
Since most cable systems in Canada are owned by one of a handful of major providers (Shaw, Rogers, Cogeco, Bell), their distribution and, critically, "simsub" (replacing US network feeds and US ads with a simulcast of a Canadian local channel carrying the same show) is generally handled at a national hub level. It's much easier to do simsub over a relatively small number of US affiliates that are fed by fiber to the national hub than it is to try to pull a US DTV signal off the air, especially once you're past the immediate border area.
And so Detroit has become the default set of US affiliates for anything in Ontario or west until you get to Pacific Time and Spokane and Seattle feeds take over, depending on which cable provider you're using.
The greater Toronto area still gets Buffalo stations because of many decades of tradition and habit, as well as a strong affinity for Bills instead of Lions, Quebec gets Burlington/Plattsburgh and the Maritime provinces get Boston.
There are very few other exceptions anymore for the traditional big 3. WUHF in Rochester is fed by satellite and fiber as the Fox affiliate even in many areas that otherwise would get Detroit or Buffalo, with some of its daytime offerings and infomercials replaced by Canadian infomercials.
For PBS, there's a little more variety because some border PBS stations have been willing to pay for fiber delivery to Canadian markets where cable once picked them up over the air. (And of course simsub doesn't apply!)
So WPBS Watertown is still seen in Ottawa, Prairie Public from North Dakota is still seen in Winnipeg and WQLN Erie is still seen in London even though the big 3 from Erie have long since been replaced by Detroit or Buffalo.
The CRTC has a list of which US affiliates are approved for carriage on Canadian cable. It also includes a small number of superstations that are generally an extra cost tier: WSBK Boston, WPIX New York, WGN Chicago, KTLA Los Angeles and somewhat unusually, WPCH-TV Atlanta, the successor to the old WTBS over the air feed. Canada always got the full local feed of each of these channels, even after WGN and WTBS split off their separate satellite feeds.