I've posted they before but some time ago I spoke to an AT&T tech who doing an install in my neighbors apartment. He used to teach electrical engineering at the local community college but preferred to work out in the field.
He told me that they were sending up to 5 TBs of data using the fields generated by the power in the lines across the city. That doesn't just stop at a transformer, and if anything, engulfs it. More than some of that will make it's way down the line to your place, to dirty up the AC.
That was years ago and it doesn't seem too much to think all carriers are doing something of the sort all over the place.
All the best,
Nonoise