Street art

The distinction is quite simple. Do you own the canvas or have permission to use it? No? Then it is vandalism, regardless of how pretty it looks.

that belongs in a museum

In this case, it's both, unless the owner of the property says otherwise

Something that takes this much time and equipment is 100% paid for by the owners of the building. So yup. Art. (But imo it would be either way. Art is art whether you want it there or not.)

A thing can be both.

This in particular is a paid commission. It is not vandalism. Vandalism can be art, but not all art is vandalism. You can normally tell if it was paid for by the quality and structure of the work.

Vart.

this is in montreal, right?

Aww it looks like a Mucha piece!