When translating the BBB-Plugin we discovered the following issue:
While everything else in the notification message can be translated, there is the word "at" (between date and time, e.g. start or end time) that can't be translated via the Moodle-interface. I suppose that this one word "at" is hard-coded in "lib.php" at lines 440 and 444 and therefore it can't be changed via the translation interface in Moodle.
It would be great to have a separate string for this expression so we (and others as well) could translate it like everything else within the administration interface of Moodle.

Reproduction:

1. Translate BBB-Plugin via Moodle-interface (at least all the strings for the notification message)
2. create or edit a BBB-conference in Moodle
3. activate notification
4. set a beginning and/or end time/date
5. see notification message and note that everything has been translated except the word "at" between beginning or end date and time