Even though it seems that the ACARS had been disabled the FMC GPS's would probably still been sending and receiving signals to EGNOS or the MSAS satellite system, are these signals traceable ?
Sadly, popular media showing people being tracked by the GPS receivers has confused too many people. GNSS (GPS/GLONASS/...) receivers do not transmit anything. They only receive. They receive signals from several satellites, and using the timing from them, calculate their position. EGNOS and MSAS likewise only receive correction data *from* auxiliary geo-synchronous satellites to make the primary GNSS signals more accurate.
Caveat: almost all radio receivers emit low level signals (leaked local oscillator, digital system clock noise, etc). This is irrelevant to their being trackable except from very close (a few tens of meters).
