They can't run through anyway as the local lines aren't electrified. For rolling stock transfers (for example when Meppel - Leeuwarden would be closed) it is possible to have NS rolling stock being pulled by a diesel locomotive use the local line to get to Leeuwarden as there is a non-electrified connection track between the workshop at Onnen and both halves of Groningen station.
The other thing the Netherlands is very good at is asking passengers to change between electric and diesel trains for maximising straight EMU running under wires.
The British temptation would be to run bi-modes or even diesel under wires, like London - Leeds services extended to Harrogate.