Carriage fees doesn't matter for mega 24 and mega musiq as both are pay channels. Mega TV network or other South TV networks don't have good distribution teams hence dth operators did not add South Channels quickly. Another reason is all dth providers are operating from roi except sun so their first priority is always north.
May distributors not happy with Airtel as you said, but most of the customers are always happy with Airtel packages at affordable prices