TRAI has issued a framework for portability of the DTH services in which they have suggested clauses to implement the portability of DTH services like mobile services, you can go through the same on following link
https://trai.gov.in/WriteReadData/WhatsNew/Documents/PR-23-01042015.pdf
However tata sky has not implemented the frame work and has suggested changes to this scheme which in only in benefit of the company, this can be seen on the comments which TATA sky has given on official TRAI site on following link
https://trai.gov.in/WriteReadData/WhatsNew/Documents/PR-23-01042015.pdf