I think the only way this gets fixed is if you create Federal consequences for the local police. It sucks putting cops in that position, but, it's the only way to circumvent the local authorities. The cops will ignore their state/local officials if they know they can be personally sued/charged for not notifying ICE.

The only other way I can see: create an anonymous tip line/site for police. The problem there is that local devices can be searched.

There is no good way to fix all of this, short of full-blown Federal legislation, that needs 60 votes in the Senate.