As per 3GPP we have 2 approach for eUTRAN sharing.
1. Multi Operator Core Network (MOCN)
2. Gateway Core Network (GWCN)
In MOCN, only eUTRAN part is shared between multiple operators. In GWCN, MME is also shared along with eUTRAN between multiple operators. So in case of GWCN, MME should have support for multiple PLMNs.