As the article points out, the Newark NJ joint-use arrangement was one of several that exist under FRA separation rules. The "deal" noted was interesting because it's about the only one I've heard of under FRA jurisdiction that didn't require the freight to run at night - of course the infrequent movement (once a week, with separate track - spatial separation, which FRA prefers - for most of it) helped. One presumes that NS had some kind of communication with LR Dispatch so the proper signals could be set at the time; freight trains like that don't run on a schedule.

San Diego could get interesting if manufacturing starts to trickle back from the Far East. First stop for a lot of it could be Mexico, which could result in more trains (or at least longer trains) wanting to go to Tijuana. Though of course trucking is more likely at least during startup. That's joint-use territory with San Diego Trolley with freight at night. Past use has been a few cars now and then - has that changed with the Toyota plant opening up a few years ago? Anybody here from SD - confirm? Also, what's the story with freight up the Santee line - does it still happen?

We all have heard about the separation setup with the Sprinter - is it working? Can freights actually clear the line in time for morning commuters?

In the Olde Dayz of course, freight+passenger coexisted routinely on interurban and some interurban-used streetcar trackage. FRA wasn't around to protect us back then . And the interurban cars had a lot more in common with mainline equipment than with streetcars/light rail anyway. A wreck between a SN car and a streetcar probably would have had about the same effect on the streetcar as if it hit an SP train.