I think one of the biggest apples to oranges cap rate comparisons is to compare cap rates of city utility park verses package plant/lagoon. The problem is capital expenses are listed below NOI. Here is an example. Two parks both have 150,000 NOI.
However park with park with package plant has 600k of additional infrastructure. Lets assume it was brand new with 30 year life (most package plant on the market have 0 to 10 years left in them). Yearly capex reserves is $20,000 higher so really to have an apples to apples comparison you should say city utility park noi 150k, private utility park noi $130k. However this is never the way thing are listed they both are listed at 150NOI then a cap rate is applied. If you fall for the cap rate mirage you just over paid by 14%.
Then there is the risk of increased regulations, and the fact that the current owner doesnt have a licensed operator and is running the plant on a shoe string budged and the actual operating cost should be lot higher than what is listed by the owner.
The risk of increased regulations demands a higher cap rate. New regulations are coming and it will cost in terms of plant upgrades and operating costs.
Just my two cents