Short Line Rail Investing

I'm interested in investing in short line railroad since they seem to be the target of a lot of State-level government grants, funding initiatives, and tax incentives and I suspect many will soon be acquired by the Class I rail operators like NSC, CSX, CP, CNI, etc. However, only these large railroads appear to be publicly traded. Does anyone have ideas about how one might go about investing in these Class II railroads? $Norfolk Southern (NSC.US)$ $CSX Corp (CSX.US)$