How do you determine what is "discarded"
During that turn Omnitron destroyed all equipment cards. Does destroying equipment count as discarded?
or does it have to come from your hand. So would that take out the police backup? or no
Discard is from hand.
Destroyed is not discarding.
If it's in play and then moves to the trash it's destroyed, if it's in your hand and it moves to the trash that's discarded.
So Omnitron's "destroy all equipment in play" is destroy, and the police live on to fight another day.
Note that there are a few cards which say "discard" without involving a hand...usually they're discarding cards from the top of decks (eg Violent Nightmares or River of Lava). I believe such effects would get rid of Police Backup. What's not clear to me, though, is exactly how optional the discard can be and still automatically get rid of the cops.
The discard effect has to trigger for police backup's "would discard" to take effect.
For example if Fixer was highest HP hero vs. Matriarch and a fowl was destroyed, and Fixer chose to destroy a card he would not get to redirect the damage that he would have taken if he hadn't destroyed a card.
In Police Backup's case you would have to choose the discard effect if it was optional for Backup to be destroyed.
If you get a "discard your hand" and a hero has 0 cards in hand and they choose to discard their hand of zero cards police backup would be destroyed because they would have discarded.
This is how I interpret Police Backup.