Sometimes I run my finger along the glass/substrate line to clean it, and I leave the algae remnants on top of the substrate for the snails to clean up because I am lazy.Can it "escape" if I pull a plant up for instance?
It never settles anywhere else despite me doing this. I believe "spores" will be everywhere in our tanks already, but it can only settle in the substrate line because thats the only location where conditions are right. In a way it is already "everywhere". A reasonably balanced tank would not allow it to grow to visible size anywhere else. Therefore mechanically spreading it is not something I am concerned about.
I must add a disclaimer that I could be incorrect about the thing living in my substrate being cyano, in which case my advice might be very bad advice.
I have assumed the ID by that it comes off in filmy sheets, it likes to live in an area of very low flow but with some light (glass/substrate line), and that it doesnt smell very nice if you put a bit of it up to your nose.