Dear Lorne Gaetz,
Thank you very much! As far as I can tell with two half week days of testing, your cid-cleanup context does the job completely.
There is one related issue with my phone provider (Deutsche Telekom, i.e., incumbent carrier here, strongly pushing for all VoIP without really willing to actively address all related issues 
): They deliver incoming national calls at random sometimes with the contry code and sometimes without. So a call from Hamburg may be +4940… or 040… with variable number length thereafter. The superfecta phonebook sources available do fail if the number is +4940… but work if the number is 040…
Is there a way to address this within superfecta or should one include this in the cleanup context to match a leading +49 and replace it by “0” if the former is matched? You have published similar examples in the pbx in a flash forum, albeit for fixed length north american numbers, I think. The details do look complicated for an outsider - could you please be so kind to drop the necessary lines for this case also?
Regards,
Michael Schefczyk