Symbol Rate is not an accurate indication to know bandwidth capacity available on transponders of an operator . There is a separate formula to arrive at it. But symbol rate can give a somewhat close idea about bandwidth available.
Actually just see how many 36 Mhz or 54 Mhz transponders both Tata Play and Airtel Digital TV have , we can estimate the number of channels it can hold with MPEG4-DVB S2 compression standard. Now there r advanced encoders deployed by these operators which further help optimize the use of bandwidth available and further by tweaking (increasing) symbol rate and decreasing FEC additional bandwidth can be generated however increasing symbol rate may adversely effect life of satellite bcoz of excessive load which consumes more fuel and even require more power from earth station to be used to maintain good signal levela. Also increasing FEC say from 2/3 to 5/6 will cause more signal loss incase of bad weather conditions.
Still if we look at above charts , Airtel Digital TV has kept FEC and Symbol Rate for both its 36 Mhz and 54 Mhz well within regular limits while Tata Play has increased symbol rates beyond regular levels on most of its 36 Mhz transponders to generate more bandwidth.
Airtel Digital TV and Tata Play r almost all same level interms of bandwidth available but Airtel Digital TV may still be able to squeeze in few more channels and still managing to air channels in good transmission quality but Tata Play cannot seem to afford to do it as it will further reduce transmission quality.
Soon Airtel Digital TV will activate new transponders and after completing formalities / contractual obligations for New RIO with various broadcasters it will realign LCN of all channels and then add new channels on the platform