Hi Zenon,
It didn't work for me either. Try creating OSS request for object /SAPTRX/LEH_BAPISF12 and it will help other EM consultants/projects too:)
While we have solution:
If there are not too many events, try using pre-processing functions instead of creating custom IDOC_INPUT_EVMSTA.
Other option is /saptrx/badi_message. As you already know, this BADI has been replaced by pre-processing technique but still works till we have a solution and you can de-active it later.
Thanks,
Vishnu