Hi, I've applied for several jobs with Network rail and their all starting to come through now, I applied for a track welders position and has taken over 4 weeks to hear something and have now been invited to an interview, the signallers job took about 3 weeks and have now been invited to an assessement on monday, so I would say normally you will hear something within 4 weeks depending on closing date and if it closes early etc.
Hope this helps.