This is not an insurmountable obstacle.

An example of how this would work in day to day operations is seen in the Tampa streetcar operation to Ybor City.

Streetcars operate daily across a CSX mainline from downtown Tampa to Ybor City and back. The crossing, on both the CSX and streetcar line, is protected by absolute signals and written rules.

I experienced an evening ride on the streetcar where the signal for the crossing would not clear, despite no occupancy by CSX in the block. The operator could not proceed across wiyhout the direct intervention of a streetcar supervisor on scene, who communicated with the CSX dispatcher by telephone and followed a specific set of written instructions in case of such an incident. All in all, the delay to cross the CSX took the better part of an hour.

I would imagine that the Museum and Metrolink would do likewise with absolute signals and written rules for this operation.

When all the parties involved can focus on the solution as needed, I firmly believe the connection will be installed and operations between the Perris Depot and the Museum will occur.