The success of this will also depend on the type of pine (or fir or spruce, or whatever Pinaceae...). It would be cool to try this with many different types of needles and make a list of which ones work and which don't. I've wanted to try this with ponderosa pine needles, but haven't gotten the chance yet, so this is really cool to see that it can be successful at least with some types of needles.
I would assume that trees used for orchid bark (including ponderosa pine and douglas fir... others?) would also have needles that are safe for growing many CP's.
Other pines that grow along with CP's in the wild would probably also work, as thier needles get mixed in with the soil over the years