the way I read 300.5(D)(3) is if the service conductors are not in concrete a ribbon is required, and PVC, EMT, as well as RMC is not in concrete or am I loosing it with my English?
I would add that in most cases these conductors would be under the utility's control and would not be subject to the NEC at least around here it wouldn't, but lets say you decide to use 230.40 exception 3 and run a second or third feed from the meter back into the ground to an out building/s then I have always been required to install a ribbon above them, I know it's been in the code since at least the 1999 cycle.
The rule here is if the SEC's are not in concrete they get a ribbon.