I was at a DOT when we first got into CAD. Most DOT's started with the mainframe based IGDS which ran on PDP 11's and then DEC Vax's. And most of us started not with InRoads but with AASHTO's RDS. We were using it on mainframes using CRT's for many years before CAD and when many DOT's looked at CAD, AASHTO had it ported to IGDS and that's why many DOT's ended up on MicroStation. One of the Bentley brothers developed MicroStation to read and write IDGS files.
And when we started buying MicroStation to phase out the mainframe CAD, we bought if from resellers, just like the consultants who did work for us.