Mountainous terrain isn't required, but it's the situation in which cable cars make the most sense because "better" options that require relatively flat ground aren't available.

Remember, the big selling point of a cable car is that it's cheap, but it's also lower-capacity than more usual kinds of transit. It's more legit than some gimmicky 'gadgetbahn', but not by much.

Not just mountainous terrain. Mexico City has one that goes over some densely packed naighborhoods. The roads are not good for buses, so the cable cars go over the town and connect to the BRT

Also works well over bodies of water.

There's a new CBC Radio article that OP may have forgotten to link to.

It does seem like there's not much of a use case if you don't have the requirement to cover a large change in elevation in a relatively short distance - mountains, or to get up and over a shipping lane, or something like that. The article argues for them to be inexpensive, which...I'm sure they are, but they seem to be relatively low-capacity, and pretty limited in terms of the number of stops you could include on a route. But I'm not an expert, and maybe I'd be surprised.

Yeah I read the same article and thought I included the link but silly me 😝 I assumed a mountainous terrain was a requirement but appears to be doable here in the GTA too. I was surprised to learn a project is already underway in the Oshawa region.