I had an interesting experience a few minutes back. I wanted to travel from Dahod to Vadodra by one of the trains. This was on IRCTC. But there was no room. So I checked Nagda to Vadodara. There was one berth available. However when I asked for Nagda to Vadodara boarding at Dahod, it refused to accept. I think they don't want Nagda quota to get misused by other stations