Canadians benefit from a major oversight in the development of the Nexus 4: despite being a HSPA+ device, it is capable of performing at LTE speeds over AWS (1700/2100Mhz) frequencies. Thanks to similarities to the LG Optimus G, the Nexus 4 maintains the same WTR1605L baseband and amplifiers capable of carrying a LTE signal over AWS.
It was by accident that the capability was discovered, and was soon flaunted as a major advantage to Canadian owners over their U.S. counterparts. Turns out the celebrations were short-lived. Due to FCC regulations, the Nexus 4 cannot legally carry a LTE signal and, in accordance with the law, Google has removed such capabilities from the device in Android 4.2.2.
Users on XDA-Developers have reported that updating to Android 4.2.2 replaces the baseband with version M9615A-CEFWMAZM-2.0.1700.48, eliminating LTE support. Replacing the new radio version with the one from Android 4.2.1 reinstates LTE, so the functionality depends on the baseband version and not the underlying Android code.
Nexus 4 owners without an unlocked bootloader are out of luck, as replacing the radio version involves voiding the warranty and messing with the underlying software.
That’s all, folks. If you want to continue on Google’s software path, you will lose LTE speeds in the process.