I think you cannot do that.
1. Mumbai Central Local Station is different station from Mumbai Central. If you want to enter Mumbai Central you need platform ticket, you cannot enter with Monthly Pass.
2. If such travel is allowed then you will see so much rush in Mail trains. :)
3. One of my friends used to stay at Virar, and take...
more... pass till Vaitarna and then used to catch Flying Ranee from Borivali for Virar. He indicated that pass till Vaitarna allows you to board SOME designated mail trains like Flying... But that was before Dahanu Locals commenced.
I feel strict NO.