Sky are struggling to make it work.
The last deal is worth less per game, and overall as well. Sky have been raising prices on their products way above inflation to subsidise the lower profit per sports customer problem they have, and one of the reasons sky are branching out into other things is they are losing confidence in football as a long term profit driver for them.
There is also clear differences between BT and sky.
Sky have been known for football since 1992, and people still see sky now as the place to go for football, they air more games and they now have the rights to all the first picks, e.g. manchester derby, it be on sky, the leics city EPL title win, all of our last 9 games and spurs last 9 games were live on sky, BT got none of them.
In terms of internet infrastructure, sky have unbundled exchanges, brought the easynet network. So own a internet core. But compared to what BT have which is a fully meshed nationwide network, they own the local loop in most of the country, wholesale provider for most isp's and even lease out connectivity to competitors like sky. The two companies are in different places and have different core sources of revenue so the importance of EPL rights on either company I feel isnt comparable.
We will know in 3 years if the EPL rights is decided to be a wrong path for BT, when the next rights come up for auction, for now they committed for another few years as an auction has just ended.