Smokey,
We will of course not come to a clear conclusion in this specific case, but just for the sake of it, let me think...
(1) the suspected pax used a blackberry
(2) only the channel called 133.8 seemed affected (in fact a window of a few KHz)
(3) all transmissions were clearly audible
(4) the interference (in this case perhaps appropriately called jamming) totally drowned ATC
Point 3 is evidence that the digital transmission from a berry (whatever sort) cannot be the cause, at least all by itself. There is nothing that can incidentally convert a digital signal into analog.
Point 4 shows that the signal was significantly stronger than ATC's, itself in essence strong (50W - line of sight).
This again cancels the berry-track, as far as the radiation of undesired harmonics or other spurious is concerned (much too weak).
I would add a point
(5) the interference took place at cruise level and lasted several minutes
Again this does not point toward a cellphone. It is possible to initiate a call under certain circumstances, but placing several calls and thereby maintaining minutes-long contact with ground cells is extremely improbable.
I might have the beginning of a small idea, but can you detail:
where was the pax sitting
front/mid/back ? and window or other seat ?
in your estimation, how long did the interference last ?