I've watched the show since 2005 but I'm not up on how much the BBC puts out false leads, red herrings, etc. Have they done it in the past? So I'd have to guess this is true.
It certainly stands to reason for this to be true. If Eccelston was participating, they would have announced it at the same time as they did Tennant and Piper. And of course he always said he didn't want to come back. I'm disappointed because I wanted to see him again. I won't say he owes the fans anything but would it have really been that much of a pain for him to be involved in this? To show up, get paid, have some fun being The Doctor again and make people happy?
The fact that he took multiple meetings with Moffat at least means that he was open to it.