We can find on Regulation 51 how the various notices we covered over the last few days (and a few others) are to be sent for publication at EU level. This communication is mandatory for contract notices related to contracts covered by Directive 2014/24/EU. However, even for contracts not covered, contracting authorities can always get said notices published at EU level.
There is not a lot to say about this Regulation other than the notices should be sent electronically and that contracting authorities are expected to keep evidence of the transmission. This should come without saying, but over the years I have always been amazed at the (in)ability of some institutions to keep easily accessible records and "paper trails" that justify decisions or can be used in times of need ("Did that bid come in the last day or the day after?").