I don't think you have a clear understanding of how simplex radio operations work. The amount of watts you have has nothing to do with how far you can receive, as other members stated that's only for transmitting.
As far as receiving fireground, I used to live on the northern tip of Greenpoint, Brooklyn. Sandwiched between lower Manhattan and south western queens. On good days I used to be able to receive fireground communications from both boroughs with a UHF 35 inch magnet mount antenna placed on a cookie sheet. I also used a UHF radio to receive, because radios always recieve better than scanners no doubt. I would find the highest spot in your home or apartment and improvise a solution for an antenna if you can get it outside, even better.