Installing OTA with Directv

Hey there,

Since it looks like our area (Rochester, MN) isn't going to be getting locals in HD any time soon we'd like to know if it's possible to 1) get an OTA antenna installed by the DTV installer when they install the dish and 2) run the OTA signal over the same coax as the Directv signal, using an a21 to integrate the OTA signal?  We have 4 TVs and all of them have just one coax line.

Thanks,

Jay