Future UTA does a nice job discussing electrifying FrontRunner. It notes that "electric traction can substantially increase the rate of acceleration trains are able to achieve, thus reducing trip times".
The benefits of doing so are uncertain, and calculating them is complex. Reason&Rail did so for the Amtrak Surfliner. He gives the number of $3.6m/mile, based on estimates for California's HSR.
Take-away is that shifting from a diesel train pulling cars (like FrontRunner) to electric multiple units doesn't seem to save much time.
However, the Surfliner only stops 8 times, while FrontRunner stops 15 times (over 17 stations). Doubling the # of stations would double the number of times FrontRunner could benefit from increased acceleration. FrontRunner is 88 miles long, the Surfliner 125 miles long. So FrontRunner probably spends less time at top speeds, so acceleration is much more important. Surfliner EMU cuts time by 8%, 1%/stop, so we'll assume FrontRunner does the same, cutting travel time by 15%. VTPI suggests a non-linear relationship, with a 15% reduction in travel time resulting in a 20% increase in ridership. Wiki says daily ridership is 17,600, so that would bet 3,520 new daily riders.
88miles*$3.6m/mile is about $315m for electrification. $315m/3,520 gives a cost of about $90k per new system rider. Which is very very high, higher than most heavy rail projects. ...and better than some light rail projects. By Montreal standards, pretty high.
Again, a back of the envelope calculation says it's not worth it. This calculation does not include pollution costs or savings in fuel costs, or savings in travel time etc, so it's not a cost-benefit analysis.