They'll have a hell of a time getting in other cities in the first place. AT&T and the major cablecos typically have an absolute, legally-sanctioned stranglehold on their markets.
But up until now there have been no clear alternatives when citizens try to fight those sanctioned monopolies.
If Google is offering 100x the speed in another city, Time Warner, Comcast, AT&T etc. will have a hard time explaining why they should retain their monopoly unless they offered something competitive.
Exclusive franchises, building permits, neighborhood associations, etc. Comcast, Time Warner Cable, and AT&T have been playing this game for a long time. It'll take fighting through tons of telco/cableco-paid for local laws for Google to get in anywhere; just because they've made it in one city won't make the next any easier (in fact, probably harder). I hope Google (or someone else) pulls it off, but it's not going to be easy by any means.
