IAD Controller described an unauthorized runway entry event involving airport personnel working near by; the reporter stating more briefings are needed for the airport personnel.

Narrative

I was training a CPC-IT on the Local Control 2/3 position during the event. OPS1 [vehicle] was on the frequency and was conducting work with the field electricians on Taxiway Q2 due to an airport sign that was damaged. OPS1 called and said 'Tower; OPS1 needs to get on the runway after SAS departs for two seconds.' We replied to OPS1 'Roger.' After SAS departed we told the next departure; an E170; to line up and wait. I looked out the window to where the trucks were and noticed a couple of them moving around and was unsure if any were on the runway or not. I then asked 'OPS1 do you need to get on the runway now?' OPS1 replied 'we already are.' I advised the Supervisor of the situation and then explained to OPS1 that we understood their request but they did not have permission to proceed onto the runway. Recommendation; I recommend that the individual driving the OPS1 vehicle take some sort of refresher training on runway safety and be re-briefed on the proper way to enter/exit the runway.