There does not need to be no property taxes on IZ units indefinitely. The taxes just need to be reduced enough, for long enough, to pay for the units. In the Portland example earlier, those property tax exemptions are for 10 years and are either for the increased property value or just the value of the IZ units. Just to make this clear,
the city does not need to spend any money, or even temporarily reduce property tax collections. They would only need to
temporarily delay an increase in property taxes. More information on the program here:
https://www.portland.gov/phb/multe
For Prop 2.5, this specific tax increase could and should be exempted. Assuming the requirement is coming from the state, that's pretty straightforward to just include it. I'm also confident if Prop 2.5 was the only thing in the way of a city implementing this, the legislature would be happy to exempt them. The usual arguments for Prop 2.5 don't apply because this is for new growth