This is basically the same scenario as if the transponder of aircraft A is not powered. There is no communication from this particular unit to any other aircraft or ground unit. Data to the acas unit are non-existent or void.
The XPDR and acas unit of aircraft A, however, are not switched off, they MAY be able to receive a communication through . Due to the unavailability of comparing these data with own data it will, however, not calculate any position or threat at all.
As Greybeard said, there is a FAIL annunciation and no further data are displayed.