I believe this phenomena was covered by an Airbus 'Flight Operations Transmission' dated 04 July 2013.
Airbus Ref: 999.0040/13
Subject:ATA 31/29 SPURIOUS Hyd B(G)(Y) RSVR OVHT ECAM ALERTS DUE TO SDAC MISBEHAVIOR.
Applicable to A318/A319/A320/A321
1.Background
Some operators of A320 family aircraft reported spurious triggering of several HYD B(G)(Y) RSVR OVHT ECAM alerts during cruise, on aircraft equipped with System Data Acquisition Concentrator (SDAC) H2 units identified wirh PN 350E550020x. These ECAM alerts affected one or several hydraulic circuits, and were not associated with the respective HYD ENG PUMP FAULT light indicators on the overhead panel'
2: Explanation
The SDAC receives several types of analogical signals, and converts them to ARINC information. These ARINC information are sent to several aircraft systems for the display of indications on ECAM system pages and for the triggering of aural alerts. These ARINC information are not used to ensure the lighting of local FAULT lights of the Engine Driven Pumps (EDP's), Electrical Pumps (EMPs), and Power Transfer Unit (PTU) pushbutton switches on the overhead panel.
Investigations confirm that the root cause of these spurious ECAM alerts is a faulty component in the SDAC H2 units identified with PN 350E550020x as per OIT REF 1.
The faulty component causes the SDAC to send erroneous ARINC information that may cause the ECAM to display erroneous information:
-One or several of the ECAM alerts HYD B(G)(Y) RSVR OVHT.
-Changes in parameters or erroneous indications on the ECAM system page 'HYD' (as described in OIT REF 1).
Investigations confirm that the ECAM alerts HYD B(G)(Y) combined with the 'OVHT' indication displayed on the HYD systems page, were not associated with the lighting of the respective FAULT lights of the EMP(s), and/or PTU pushbutton switches on the overhead panel.
3. Operational recommendations
If the HYDvB(G)(Y) RSVR OVHT ECAM alert(s) are triggered and combined with:
-An 'OVHT' indication displayed on the HYD system page
-The lighting of the respective FAULT lights of the EMP(s), and /or EDP(s), and/or PTU pushbutton switches, then
the flight crew must complete ECAM alert(s)
If one or several HYD B(G)(Y) RSVR OVHT ECAM alert(s) are triggered and combined with:
-An 'OVHT' indication displayed on the HYD systems page
-No associated lighting of the respective FAULT lights of the EMP(s), and/or EDP(s), and/or PTU pushbutton switches, then
The flight crew may suspect SDAC misbehavior (as described in this FOT and OIT REF 1) and can consider these alerts as spurious.