HCC has "provided" about 5M cpu hours over the last year, and used about 3M away from Nebraska. We still win due to larger context issues (and the utilization of otherwise idle cycles via backfill).
It would perhaps be interesting, however, to revisit the idea of somehow giving sites some sort of "credit" for providing resources -- it could make it easier to recruit new providers if they knew they'd be able to somehow recover the resource they provide. However, I have a hard time finding a clear way to do so! Opportunistic is clear. We benefit from that substantially. Without dedicated resources to leverage, it is not clear how one would "credit" a provider beyond current rather indirect means.