As per specification a cell can broadcast up to 6 PLMNs. First plmn in the list is known as primary plmn while others are known as secondary plmn. Theoretically an eNodeB can support up to 255 cells but I never heard this number for a deployed site. In case RAN sharing there might be possibility that eNodeB is being shared. Theoretically maximum numbers can be calculated i.e 255 * 6 assumed each cell serving different set of PLMNs but it is not realistic number.