The best answer is that it depends. First, if you do not have cable TV service then the odds are very high that your service has been physically disconnected outside of your home. However, if you're like me and only have Internet service because your cable provider is the only broadband player in town, then the odds are pretty good (at least they used to be) that your cable provider is only filtering (inserting a filter device before it enters your home) low-end of the RF where all the analog channels reside.
The FCC mandated the cable companies to provide the broadcast network (ABC, CBS, FOX, NBC) in-the-clear, and for a long-time the cable companies weren't replacing the old filters at each residents: time and materials issue to replace tens of millions of these filters...plus, most people didn't have HDTVs with an integrated ATSC tuner, a lot of people don't know they could do this, and it wasn't costing the cable company a dime and and the broadcasters weren't complaining.
I don't know if things have changed recently, but my local digital broadcast channels still come through the filter even though I only have Internet service. Of course, I have two OTA antennas and Dish Network so don't need them...but they are still there in-the-clear.
As for the digital cable channels...those are all encrypted and you'll still need a cable STB or an HDTV/Tivo with CableCard to view them. Since the former service was disconnect, I doubt you will have anything but a dead line. However, if you plug in an analog TV (NTSC tuner) and can see a few channels above channel 69 or so (even fuzzy is ok), then you may be able to lock-on to in-the-clear QAM local digitals when you get your HDTV.
Good luck...
