Shrews are opportunistic creatures.
Shrews hunt/travel/frequent vole as well as mole tunnel networks. They also travel through the grass cut trail networks made by voles. Traveling from hole to hole as do the voles. Being so small, I believe they utilize the cover of the lawn networks and mole tunnels taking advantage of the security that both habitats offer them in order to remain as covert as possible.
I have caught a few thousand in my lifetime in working voles and moles. I have caught them on the surface vole runs chewed through lawns and in mole tunnels under ground as well as in homes. They are a very versatile and adaptable specie. They are in my experience omnivores but also very good predators. They will eat meat, insects, vegetation and become scavengers as circumstances dictate. In my experience they are kind of a miniature version of todays coyote.
They climb very well in structural areas also indoors.
If you trap voles or moles with certain type sensitive trigger type traps ( both snap and Albano style traps ) you will catch a lot of them the more you trap moles and voles. I catch them very frequently doing both types of control work, at least in SW Pa where I do most of our primary service. Not any way of avoiding them when using trail/blind setting methods.
Some geographical areas we catch more shrews then other areas for one reason or another.