We would like to measure grid voltage. Can we get this from EMS?

Yes, according to 50463 (2017) part 4 also additional information which is not mandatory can be included in so called reading block.
Reading block is not part of compiled energy billing data (CEBD). CEBD should be sent unchanged from DHS (on- board) via DCS (Data Collection System, on-ground, e.g. DB Energie server) to the exchange server (EREX).

Reading block may be read und imported by any other system for energy management or other purposes.