Two things:
1) If your rigs are emitting enough RF "noise", then it wouldn't be that hard for VZ techs to find the source.
2) 835 MHz != 850 MHz. I know the numbers look like they are "close" but not when it comes to RF. Look at how many
channels we have for Wifi. The non-overlapping ones are 25 MHz apart (same as 835 to 850). You can have two wifi networks running right next to each other, one on channel 1 and one channel 6, and have them work perfectly.
I too call BS.
The noise might not only be generated at 835MHz, it probably has a peak at 835MHz with a rolloff to adjacent frequencies.
Even if it does only emit at 835MHz, the band-pass filters for the equipment that communicates with those voice frequencies are only made to block out unwanted frequencies up to a certain amplitude. You can, for example, generate a white-noise machine that makes all FM radios in the area useless by using a 100MHz oscillator with an amplifier, simply because the filters used on the radios aren't designed to anticipate a white noise source right in the middle of the frequency range that is so much stronger than the signals from radio stations.
Your wifi network example only works because the equipment was designed with that use case in mind, plus each frequency range has a buffer zone to avoid significant pollution into the adjacent ranges.
So no, it is not BS.
Seriously, just deal with it. Block the EM noise yourself if you want. Now that you are on their radar, if you don't fix the problem by either using adequate shielding or turning it off, you will eventually get the FCC involved along with a court order.
This isn't even something worth fighting on principle. These laws exist for a reason. If there wasn't strict regulation of EM interference we wouldn't be able to use all of the modern wireless technologies today without a lot more problems. The little boys telling you to ignore this are just being childish jackasses who aren't knowledgeable enough to have a valid opinion.