Having flown (professionally) for (too many) years, most aircraft departing from BUF, that would be aircraft flying higher than 18,000 feet will get turned over to an ARTCC. The would initially be ZOB, Cleveland Center, and if they're going east after a short time then on to New York Center. If you want some accurate info on freqs for the ARTCC's the easiest way is to take a look at an (IFR) enroute chart (low altitude). If you look near BUF You'll see a blue colored box. Inside the box is the word "CLEVELAND" and under it are generally two frequencies. One is VHF, the other is UHF (for military). The closest to BUF is Dunkirk 125.2 MHz. But keep in mind, you may only hear the aircraft. You probably wont hear the Center Controller. You should be able hear aircraft in excess of 100 miles or so. If you listen for the aircraft callsign, and follow it as he's handed off to other center controllers, you can listen for quite some time....
Most (but not all) of the transmitters, by the way are co-located with VOR sites. This will give you some indication as to a somewhat exact location of the TX.
The Enroute High Charts will not display the ARTCC Freqs. just the low charts. A good way to look at the current charts on on the website Skyvector.com. In the upper right, you can select the charts you want.
Hope this helps.
Best.