@uplinker
CRJ primary flight controls are mechanically signalled from cockpit to the PCUs - cables (mainly) and rods and levers - no computers involved. (There are electronics with pretty limited capabilities involved in the command of the Hstab and the spoilerons, bot not elevator, aileron or rudder). Also, both elevators are powered by dual hydraulics, so a single hydraulic would not prevent control on one side. (But see below)
Regarding the trace you comment on. Be very careful looking at left-right differences in FDR data. Often, as is the case here, left and right parameters are recorded asynchronously. The little dots show the actual data points - the lines are merely conjecture by 'joining the dots'. So in cases of rapid movement, the lines can appear to disagree because each is "cutting the corner" between mislaigned data 'dots'. As a result I would tend not to worry about any "spikes" where only one or two data points seem to disagree - you don't actually know what the position of the other elevator is AT THE SAME TIME. Both may be in step with each other for all you know.
There are two places where there seems to be a split between the traces - shortly after the point where the overspeed warning started according to the trace. It is possible that hinge moments on the elevator at high speeds and (relatively) high deflections at that speed slightly limited the elevator one side more than the other. There's no evidence of any hydraulic failure (we ought to have a warning I suspect, which no-one has yet pointed to, either on FDR or CVR) but IF such had occurred and affected a PCU on one side only, MAYBE that might explain HM limiting on one side only. But there can be other causes for that, including small amounts of sideslip, or roll, affecting the forces on each tail differently. Without some direct evidence of a hydraulic failure, I wouldn't conclude one from the elevator trace, personally.