There are some links about using of regular expressions in general:
Artist sortieren mit "The"
To avoid unwanted side effects I would not use the special Mp3tag system field _ALL, but the one and only tag field resp. Mp3tag system field which can carry the string in question, in your case it seems to be the _FILENAME system field (or the TITLE tag field?).
So your "replace using regular expression" action could be ...
Field:
Regular expression: (Prod. By .+)
Replace matches with:
Good luck!
DD.20091205.0934.CET