If EP have kept quiet about every question they have been asked so far then I don't think they are going to come forward now. And if this is proved not to be Sheila's writing then I think going to the press will make the CT team look bad. Just get it tested first. if they know the source definitely, then I think to raise the money would not be difficult , but I don't think they do.
Oh dear,putting the cart before the horse is never good really,unless there is a strong argument about it being Sheila's handwriting,which can be compared by a mere layman if there are other letters to compare them to.
I don't really understand the use of forensics to carry out this task though,except that it would be a guarantee that they were authentic using a signature of proof.