My guess would be that they were short on space at Cahill St. as they were rebuilding the depot tracks at the East (Geographic South) end. At that time, the city was rebuilding and widening the Park Ave. underpass which required the construction of a shoo-fly to the East starting behind the then studios of KNTV.

The other possibility is that the Espee was known to use the subs on freights when they had a shortage of cabeese.