Unfortunately no. Their support page for this question has posted incorrect information. With the Fantasy Football TV App, you can only track your players if you have a league set up with NFL.com. Yahoo! sports, ESPN or other fantasy websites do not work with the DirecTV Fantasy Football TV App. I have tried everything and customer service says they are working to correct their website (on the Support Q&A pages) to provide correct information.
If you have purchased a Cinema Connection Kit (CCK) to hook up to your DirecTV receiver so that you can have Internet access with your DirecTV receiver, call and request a refund. If you have the CCK for the purpose of the other TV Apps, then enjoy. However, if you are like me and wanted the luxury of live updates via the Fantasy Football TV App, it only works if your league is set up with NFL.com.
There is the Channel 701 Player Tracker system built into the Sunday Ticket package, and I have not had the chance to see exactly how the "live" notifications work with it. I have it set up for games this Sunday (9/8/13) and I will report after the games to see how the Player Tracker system works. You can only set up 2 teams (9 players each), which lets you put in your weekly fantasy players (1 QB, 2 RB, 3 WR, 1 TE, 1 K, 1 Defense) for each team. 18 players total. The issue is that you have to update (drop players/add players) each week, while on the Fantasy Football TV App, my impression is that once you update your fantasy football roster each week, the TV App would automatically update with your changes. However, that will only work if you have your fantasy football league set up through NFL.com.