On a cost per mile full life cycle basis the electric locomotive would have lower per mile O&M costs, despite being more costly/offset by longer life. No prime mover, means way less maintenance costs, and longer service. But, electrification is very-very-very expensive, and adds to maintenance costs of the electric distribution system and overhead to power the train.

The fact is that you do get better operational performance with an electric locomotive or train, but without much "monetization" of that benefit to offset the costs, to the operators. You can buy an awful lot of diesel locomotives with just the interest on the huge capital cost of the electrification investment.

The fact is also, that with today's tier 3 and 4 locos, electrification becomes a very expensive reduction in health standard and greenhouse gas emissions, on a "cost per ton" reduced basis, compared to way cheaper emission reductions, that are way more cost effective, and even save consumers money.

While Caltrain electrification is moving forward and is going to happen, it will probably be, at best, a wash, in terms of the costs versus the incremental increases in performance, and lifecycle equipment savings. So, the Caltrain electrification is and has been largely a political decision, couched in terms of better performance and/or air quality. But, it is not necessarily a decision based on good "economics".