Does a brand new electrical circuit for audio gear benefit from burn in/break in time?

no.

I just moved my “A” system to a new room and had two new 20A dedicated lines installed . All the goodies …. New Armoured electrical cabling from the panel, new top model FURUTECH electrical outlet plugs, ..and with already run-in CARDAS CLEAR power cables ….in an established $40K audio system.

my experience: after running it for a month, I don’t see any noticeable difference in the electrical system from new even with a “run-in” time. It’s not the same as a run-in on analogue cables. ( at least for me ). No brightness to start, no brightness now.,, no nuthin’ better or no worse from new.

With the mutha size power supplies in my gear, I follow OEM mfg recommendations to NOT use a power conditioner. Installing another Intermediary “filter” in the linkage MAY have a bespoke effect , depending on the PC unit and your bespoke system. ( I’m not suggesting it’s gonna be either good or bad ,,.)

FWIW

Without question it does get better give it a week ,just like speaker cables 

and use good gold copper outlets the garbage that are on your wall is $3 

 buy good outlets and always copper,never aluminum wire !

I noticed an immediate initial improvement but noticed no "burn in."