I interpret Abitibi-Temiskaming as being a single region, bisected by a provincial border.
In Northwestern Ontario, we don't refer to the region where Thunder Bay and Marathon are located as "the coast", and we often laugh when people call it that. It's the North Shore, and North Shore is a very common name for things up here. (In Wisconsin, they're south of the lake, but refer to their shoreline as "The North Coast"). To us, "Coastal" is the Hudson and James bays.
Northwestern Ontarians have regional names for general areas, they just aren't common to people down south. The area around Kenora is the "Lake of the Woods"; it doesn't just refer to the lake itself, it's the region around the lake. Kenora District north of the Albany River is the Patricia District, a former district of the Keewatin Territory which was added to Ontario in 1912; the term is still used today to refer to that part of Kenora District (often as a hyphenated name—"Kenora-Patricia"—or on it's own: "The Patricia Portion").
Between Thunder Bay and Fort Frances is "Quetico", which includes the town of Atikokan.
From Kakabeka to Algoma, along Lake Superior, it's The North Shore. Northwest of that is Nipigon (and Wabakimi further northwest), due north is Greenstone, northeast is Manitouwadge. North of those three regions is the new Ring of Fire. Sometimes referred to as the Matawa Region as the First Nations there are part of the Matawa Tribal Council of NAN.
Ontario's far north is largely covered by Treaty 9, which is governed by the Nishnawbe Aski Nation (which is Cree for "First Nation Nation Nation", btw
) but also known as The Lowlands or the Far North. That region's northern limit is the Hudson/James Bay Coast.
These aren't widely known terms, but they are used to some extent.
The Ojibwe word for the area around Lake Superior is Gitchigaming (the lake itself is Gitchigama, or some variation of that) and that word is relatively common around here.
Stateside, Duluth is Fond-du-Lac (bottom of the lake); Thunder Bay was Tete-du-Lac or "Lakehead", a common name not just for the city itself but for, generally, the entire Thunder Bay district west of Nipigon Bay; though it is also used in Duluth to some extent. The official North Shore of Lake Superior is from Duluth to Sault Ste. Marie. The south shore is also from Duluth to Sault Ste. Marie, but opposite the north shore. No one refers to any kind of west or east shore as far as I've ever heard, but the terms "Superior West", "Superior North" and "Superior East" are used for political and meteorological purposes.
Part of the Iron Range also extends into Canada. Atikokan to Thunder Bay is generally thought of as the northern edge of that feature.
From Thunder Bay to Nipigon, there are many canyons, so that area is called Canyon Country.
I'm sure other regions of the province have names like this, it's just a matter of making the more well-known and accepted terms more widely recognizable.