Probably ad-hoc. While working at Express Jet I encountered a similar situation and we tried calling the flight plans into FSS but the sheer amount of releases pretty much showed that to be almost impossible. Consider at the time there were 30-40 departures from IAH alone, the amount of time it takes to read off the necessary info, and you get the idea. The connection was restored while the majority of us still had hair.
What's the point of an open door policy if inside the open door sits a closed mind?