Sun TV group has not offered its bouquet of channels to both ZEE and Tata Sky. When I checked with Sun TV Network on phone they said they are offering their channels to either of them and no decision is taken on this subject. sun TV is going to have its own DTH and hence there is conflict of interest in offering their channels to rivals.
THe above article mentions only STAR and Zee and hence I believe this aspect is not well known as these are south indian language channels and therefore not considered to be of as much importance as Hindi language channels.