Chances are that number was just something thrown around by someone who didn't take the time to analyze how many channels would be needed. When you also add in how NYC is right next to Philly, who's right next to Baltimore, who's right next to DC, that adds in more channels that would be needed. (and then in the opposite direction you got the Hartford-Providence-Boston cluster of channels) And with the land mobile use for first responders, you can't use channels 14-16 in NYC, 19-20 in Philly, 17-18 in DC and 14 and 16 in Boston. Sure you can share channels, but the thing is most of those independents in major cities are already leasing out their subchannels for infomercials and ethnic programming and they wouldn't want to give up that revenue. As for VHF that wouldn't really be viable for mobile broadband, considering the larger antenna requirements for VHF are opposite of the current trend when it comes to the size of mobile devices, especially if you want to overcome the RF noise that affects VHF-lo.