Suggestion: In my opinion, assuming your layout is set-up for right hand running, all that would be required would be a dwarf signal (on the ground) at the cross-over switch-points, and then another dwarf signal (on the ground) at the switch-points for the branch. The advance signals would be the key to such an interlocking set-up.
Also, again assuming your layout is set-up for right hand running, that cross-over should be layed-out in the other direction so that any train running from left-to-right on the "outside track" would be able to cross over and enter the branch.
