This article is from the Digital Broadcast Satellites FAQ, by Brian Trosko firstname.lastname@example.org with numerous contributions by others.
Yes and no. The dishes are. The receivers are not.
Theoretically, you could have a dish, a DSS receiver,
and an E* receiver, but you would not be able to watch
programs from both systems at the same time, for the very
simple reason that the satellites for each system are in
different orbital positions.