While I'm still saying that it's probbaly Angela Patrelli with the help of Micah and Molly, I think that Micah alone as reble could be done in such a way to make it at least mostly believeable. Imagine; Micah is sitting at home one day "talking" to his computer and for some reason or other he stumbles across his own name and detalis in the online government files. He then 'asks' for them to be deleated and spends the next few days/weeks (however long the time is between the abductions and when rebel first starts sending messages) studying these government files - remember he wouldn't even have to try to hack through government security, he has been seen using his phone to casually ask traffic lights to change - and then he decides that he's got to do something about it (he's always said they should use their powers to be heroes) from there he hacks into CCTV so that he can have eyes everywhere and from there has started pushing people togeather so that they can fight back.
I mean, what has reble actually done? So far he's sent few inspirational text messages. Told Clair to go save Alex - which would have been the obvious thing to do for anyone who's had a good look at the goverment's files "hmm they're sending someone to pick up a super, and he works quite close to the one person who would be willing to help and has limited imunity"
Apart from that he's hacked the goverment computers to stop the bomb and shut down the power in building 26. None of this would be overly taxing for a child genious who can make computers do what ever he wants.
The only thing that makes me think that it might not be him alone is sending Hiro and Ando to save a baby, that to me smells of someone who has some knowlege of the future, unless of course he actually meant for them to help Matt sr, but the ended up with the wrong one somehow.