No, LTE interference cannot explain the phenomena outside of a 4G area as is being described here.
Then it is likely there is a hardware design flaw that is causing it. I consulted with an acquaintance whom is a mobile device engineer for a phone manufacturer (essentially, he helps design hardware in phones, although not HTC).
To put it frankly, GPS is not some complex new technology that just was developed like LTE. GPS has been used by government and military for decades now, only with more recent iterations being reduced in size and made available for public use, which is still not that new. As a result, the supporting firmware with a GPS receiver on a phone is nearly identical on all phones having a standalone GPS, as the receivers themselves are nearly identical from phone to phone. Because of this, you RARELY see firmware tweaks/updates for GPS on any smartphone.
As I previously stated, the issue causing the Thunderbolt to reboot repeatedly was linked to a prioritization issue in the cellular radio firmware alone. It is entirely possible that the hardware configuration of the radios (cellular, WiFi, Bluetooth, aGPS) encounters other conflicts relating to power.
The symptoms of this would be reduced cellular/WiFi signal, Bluetooth interference (static on a BT headset), or weak GPS fixes. Yes, that is a LOT of variables, SINCE ALL THOSE PROBLEMS, COLLECTIVELY OR INDIVIDUALLY, CAN BE CAUSED BY OTHER FACTORS, which makes diagnosing it properly exceedingly difficult.
WiFi is the hardest to diagnose in its most common use because even with a weaker signal, 802.11n connections are designed to minimize "dead-zones" on outbound connections. Its easiest to diagnose via MHS or other wireless hotspot interactions from a connecting computer, as inbound connections fall victim to weaker signal easier.
I have often wondered if the battery cover antenna idea was genius or foolish (if it is related at all), since it seemed to be too easy to malfunction due to outside influence. If the hardware design is the culprit, there will be no software/firmware updates that fix something of that nature.