As a general statement, DBI uses cellphones for company comms. That's why you don't see antennas on the vehicles. DBI now is the major interstate maintainer contractor statewide but doubtful it has 100% of the road maintenance contracts. There probably are some exceptions within the state. That being said it does not mean that the current DBI policy never will change.
FYI this DBI subject has been discussed previously by posters on the VA forum. Do a RR search on the subject to read past posted comments. There is NOT one statewide contract for all interstates' maintenance. Each contract awarded to whomever will be to a certain length of interstate to maintain based on the state's current requirements.