The gaps are positioned between two PC ties. There is little likelihood they will ever close up and short. Only gaps that are tied to wooden ties that are bound to the roadbed and substructure that can be affected by expansion and contraction due to humidity changes will need an insulator in the gaps.
Any placement of gap filler is purely a cosmetic function with regards to the frogs for the turnouts (though that can be important for many).
-ed-
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-ed mccamey-
COSLAR RR -
http://www.coslar.us/NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.