Just so there is no confusion here: LTE works fine on build JDQ39 (i.e., 4.2.2), but it does not work with the newest radio (i.e., 0.48). So, you need to be running 4.2.2 plus a radio older than 0.48 for it to work. In addition, don't foreget that you need the proper LTE APN settings for your carrier, an LTE compatible SIM, an LTE data plan, LTE provisioned on your account, and of course, LTE coverage.
Note that some users on T-Mobile have been having issues when running 4.2.2 with an older radio on the T-Mobile network. (The Canadian carriers have no issue, neither does AT&T.)