Date: 202012
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Distraction; Confusion; Communication Breakdown; Time Pressure
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance
Contributing factors: Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: I went into the control room to relieve the RX2 Controller at XA00Z.  I received a position relief briefing and there was nothing out of the ordinary that was given to me.  There were a couple of frequency notes given to me with ZZZ1 [Center]; but other than that there was nothing different from normal.All during this time apparently ZZZ2 [Center] was ATC-0 and we in Area X were never told about this going on.  When I came in that evening there was no notice; and no one was told that a Zero event was going to be taking place.  The Controller on RX2 that I relieved was never briefed about ZZZ2 [Center] being ATC-0.  When I took control of the position I had Aircraft X on frequency and he was turning towards ZZZ [VOR]..ZZZ [Airport].  This is the routing that per the LOA we give to ZZZ2 [Center].  The aircraft was level at FL340.  After a few minutes I gave the aircraft a crossing restriction to cross ZZZ [VOR] at 100; what we give these aircraft again per the LOA.  His route of flight was going to clip Airspace X if the aircraft stayed up high before meeting the restriction.  I placed a PVD [Plan View Display] on Airspace Y that auto-directed to Airspace Z as normal for that time of night.  When the aircraft started to descend the point out had still not been accepted; so I called to the sector and got no answer.  I tried a few times to no avail.  I then tried to call ZZZ2 [Center] Airspace X and got no answer from anyone.The Controller on the low side RX1 said the Shout Lines with ZZZ [Approach] were down; maybe the ZZZ2 [Center] lines were down as well.  By this time I had hollered for the FLM to come down and explain if they knew what was going on; and it was then I was told that ZZZ2 [Center] was ATC-0.  At this time the aircraft had already entered ZZZ2 [Center] airspace without approval; and my main focus was to handle the aircraft towards ZZZ [Airport] approach.  We pulled up the approach plate at ZZZ [Airport] and I told Aircraft X to maintain 110 to not enter approach's airspace and gave the aircraft I think XYZ.AB to switch over.  Not two minutes later; ZZZ2 [Center] comes back up and helps me with necessitating the hand-off.  Not at any time was anyone working traffic aware of this issue with ZZZ2 [Center].  After this aircraft handling was done; I called Area B controllers and asked if they knew about the ZZZ2 [Center] Zero event and they said no that they had not heard anything.  Area B also is adjacent to ZZZ2 [Center] airspace.Later the FLM came back down to let us know the ZZZ [Approach] lines were back up and running.  This makes this Zero event even more frustrating to us in Area A since the routing and altitude that we give ZZZ2 [Center] aircraft going to ZZZ1 Approach requires us to call ZZZ Approach for a Point out.  So during this Zero event; we had no clue that we were actually in it; and then if we did know we would have had to do extra work just to get the procedure to work with ZZZ Approach.Another part of this is that the controller on RX1 never knew about this event as well because he had a ZZZ [Airport] departure at FL230 during this time as well; and according to the ATC-0 procedures we are to Radar Identify the aircraft when they come over to us.  I cannot be sure that this was done.  This aircraft... I don't recall the numbers or where he was headed.   Communication is a big deal in what we do.  It is highly irresponsible to not be told about something as important as an ATC-0 event in the facility.  All I needed was to know was who and when and we could have handled this situation the correct way.  We have routing for this exact situation; we have the procedures posted in the area; but if no one tells me what is happening then this type of event will continue to happen.




Synopsis: Center Controller reported an ATC Zero event at another Center facility resulted in communication issues and an airspace violation.