I had the same issue yesterday when eHRPD appeared in my market. I was at the Sprint Call Center in Albuquerque looking to see if I could find LTE there like the one in Denver. That's when I noticed I was connected to eHRPD. I assumed it was just at the Call Center.
However, I stayed connected to eHRPD at the first site and the next and the next. All the way home, 90 miles away. And checked all my LTE devices at home and they were on eHRPD. It makes me wonder how long it actually has been on.
Robert via Samsung Galaxy S-III 32GB using Forum Runner