This PLR might help:

https://www.irs.gov/pub/irs-wd/1035003.pdf

Maybe this is a one-time payment, for all the REC's that the system will generate over the years?  (And I don't think they have to involve anything going into the grid.)  Other references indicate that the 1099-MISC was used in previous years.  Did he actually receive $15K?  When?  Does he expect to receive more in future years?  

I would first ask the utility why they decided to use the -NEC and not the -MISC or even the -S.