There could be another reason that Honeywell was "invited" (that sure is one invitation that would be hard to decline) to participate in the investigation.
It is possible that the ELT was damaged by fire and the investigators need help in determining if it started/accelerated the fire or more likely was just a casualty.
Having very modest knowledge of fire/arson investigation I know that one of the harder calls can be cause and effect:
Did old house wiring start the fire or did it short as a result of the fire?
In both cases the wire can have similar features including melted "beads" etc.
Unfortunatly it is easier to just say "bad wiring" and stop rather than dig deeper, especially in cases where arson is not suspected.