Communication has been all too spotty across much of New York City and New Jersey since Hurricane Sandy struck the region, and those who can get through on their cellphones have found themselves on particularly crowded networks. AT&T and T-Mobile are providing some much-needed, if temporary, relief: the two have struck a deal to share their GSM and 3G networks in the area with no roaming fees or plan changes while the networks come back, with the best-functioning network taking precedence in any given connection. A return to the