Some enterprising tinkerers on the XDA Developers forums are demonstrating that despite the lack of a working signal amplifier and filter in LG’s Nexus 4, it’s still possible to force the phone onto an LTE network from the phone’s debugging menu — at least on LTE band 4 (1700MHz and 2100MHz) on Canadian carriers Telus and Rogers.
Last week, Anandtech reported that "Band 4 (AWS) could essentially be supported with the power amplifiers and transceiver that already are onboard the Nexus 4, but again it ultimately comes down to a particular OEM choice whether these get supported." As we've written previously, getting LTE support across multiple carriers across the US and internationally is a minefield, which is why Google chose not to include support for multiple LTE bands on the Nexus 4.
Turning back to the US, AT&T is licensed to operate on Band 4, which holds some promise for getting things to work south of the border — eventually. We've had no luck getting an LTE connection on AT&T's LTE network as it's deployed on the incompatible Band 17, while Verizon's LTE network runs on the equally incompatible Band 13. AT&T has in the past said it plans to utilize Band 4 for LTE networks, but it's not clear when or where that'll happen.
T-Mobile customers, on the other hand, may have more luck. We already recommended the Nexus 4 as the best pick for the LTE-less carrier, and as it plans to launch LTE on Band 4 soon there's a good chance of unofficial LTE compatibility further down the line. "Unofficial" is the all-important word here, though — just because the phone "works" on LTE there are no guarantees about performance, battery life, or reliability without optimization on the carrier side, which the Nexus 4 presumably hasn't received. There's also the issue of legality — the FCC approved the Nexus 4 for use on HSPA+ networks, not LTE. While we doubt the commission will be breaking down users' doors any time soon, it does mean that Google may have to push a patch to disable network switching.
Update: AnandTech has just completed a rather extensive test of the Nexus 4's LTE capabilities. Band 4 LTE appears to be fully supported, but other bands that run on similar frequencies, such as Band 1 (widely used in Japan's LTE networks) will not work. For a full analysis, complete with all manner of graphs and tables, head on over to AnandTech's report.