It can be done via VehicleRoutingActivityCosts.
Now the service time of a TourActivity can be obtained by
activityCosts.getActivityDuration(activity, arrivalTime, driver, vehicle)
Note by default it is equal to
as it is set in WaitingTimeCosts.
You can also check out #199 and #151.
I am not sure if this will be faced with the issue you mentioned, though.