Can the MEL be equal to MMEL?
I am no authority on the topic, but I'll at least try to summarise the bits from comments:


MEL can contain additional items not on the MMEL only if:


They concern after-market modifications or additional equipment and the corresponding STC permits it. Typically this includes things like IFE, wifi-routers and similar items for passenger comfort, not necessary for safely conducting the flight.
Sometimes it might be possible to add a normally required item if additional equipment is installed that can work as a backup, subject to overseeing authority approval.

MEL can omit items from the MMEL if:


They concern optional equipment that is not installed on the particular aircraft.
The operator chooses to omit them. This can be done because the associated restrictions would not allow the plane to complete the typical mission profile with that operator anyway or if the operator considers the restrictions to be too much trouble for what they are worth (e.g. would require otherwise unused procedures that would have to be trained).



If all those categories happen to be empty, the MEL will be equal to MMEL.