Of course it's plausible. The correct question is whether or not it's accurate. I found traces of evidence that support Poulson's story. I agree that Mom's admissions that Ashton played the part of Tyrone is damaging. Tyrone's voice and the recorded voice of the bomb-hoaxer are "the same" to my untrained ear - and Mom saying "other people sound like him" is a lame dodge. Of all the hackers in the world, the one who hacked my son's system happens to sound just like him! ROTFL. About as credible as your assertions that months of detention w/o indictment/information is not out of the ordinary.
This also takes care of the certification, or taking the case out of the hands of the state. Under 18 USC 5032, the feds are required to allege (3) the offense charged is a crime of violence that is a felony [check, this one is] and that there is a substantial Federal interest in the case or the offense to warrant the exercise of Federal jurisdiction [this seems to be a question of discretion in juvenile bomb threat hoaxes, seeing as how so many of them are perpetrated each year].
It's entirely conceivable that the juvenile information was filed back in March, and that all delays in getting to trial are accounted for by the defendant agreeing to delay. That would leave "relocation from NC to Indiana" as an unexplained element.