rudderrudderat,
FCTM NO-040 P10/12:
"..The APU bleed may be used with packs ON, thus maintaining engine performance level and passenger comfort. In case of APU auto-shutdown during take-off, the engine thrust is frozen till the thrust is manually reduced. The packs revert to engine bleed which causes an increase in EGT to keep N1/EPR." (emphasis mine)