I'm familiar with the Sir Adam Beck plant, I grew up in and live in Niagara County.
Not everything produced by the NYPA goes to munis. There is a lot sold direct to businesses; last I checked roughly 5% of the generation from the Niagara Power Project is allocated for businesses in WNY in a 30 mile ring. ( Although a sizeable chunk of that goes back to the wholesale markets because there aren't enough qualified companies to take it. )
I can guarantee that some of that power ended up with you. Every commercial supplier in NY buys from the wholesale market at some point, and a lot of NYPA power ends up there.