'Formats' are as seen in the Communication Monitor, where we display the actual binary conversation between the server and the meter.
It comes down to 'protocols' rather than 'formats'. Typically, the server sends a request, and the meter responds with a reply. On most meters, you first have to 'log in' and be authenticated before you can proceed. There are also sometimes additional special algorithms when setting the time, or other operations, that are typically specific to the model of the meter or the manufacturer.
Itron is based on their own flavor of DLMS/COSEM.
L+G and Elster are based on IEC61107. To get the specifics of the Elster protocol, we had to sign a non-disclosure and buy the protocols from them, so we cannot divulge any more than that.
(L+G also supports DLMS, and we use that for a few operations, but generally we use the IEC, since that is compatible with the widest range of ZMD, ZMG etc meters)
The newer Hexing meters are based on DLMS/COSEM as well, the older ones are based on DL/T645, a Chinese protocol. The concentrators, old and new, are based on similar Chinese protocols.
The Hexing DLMS is more standard than the Itron DLMS, but it is still not quite vanilla.
DLMS has some leeway in the formats of some list values, in the format of the 'question', in the meaning of the event codes, and the OBIS codes of the (one or more) event logs. So the reality is that you have to implement the protocol differently for every DLMS meter out there. It is not a matter of plugging out one DLMS meter and plugging in another manufacturer's DLMS meter into the same protocol connector.
The same with the IEC61107 implementation. The L+G and Elster implementations are different. Even between different Elster meter models, the implementation is different.
One Protocol that solves this problem, is the SyM2 (squared) protocol. With this protocol, you can generally plug in the meter from different vendors into the same Protocol implementation. Cape Town municipality has some of these revolutionary meters.
Hope that helps...