There's an awful lot of situations where concrete bearers can't be used for switches and crossings, due to the nature of the track layout. In the 80's? when York was being remodelled, the south end was done with concrete bearers, because the main route was straight. The north end was done on timbering, because both routes were on opposing curves.
Concrete is only used where standard with the standard components, unless things have changed, in the intervening years.