I have a motif ES 7 with MLAN. Can it be used in Cubase 8 pro?

That is not the question. Cubase Pro 8 can use any ASIO driver. The mLAN system that the Motif ES used was definitely an ASIO driver. The question is can the mLAN ASIO driver run on the computer operating system you need to run Cubase Pro 8.

The problem is the last mLAN driver was released in released for Windows XP and for Mac OS 9.2
I don't think you can run Cubase Pro 8 on either of those platforms. So the answer is no, sorry.

Is it the same as the XS articles? Can I use the MLAN port and will the software vST editor work?

Sorry, no again. And there is no VST Editor for the Motif ES. Back in 2003-2007 when the Motif ES was out, the Motif VST Editor was not yet available. The ES used a Studio Manager version of the Editor. It could not be hosted directly in DAW's. With the release of the Motif XS in 2007, the VST Editor was introduced and it could be fully integrated into Cubase without the Studio Manager host application. And not only that it could take advantage of the advanced routing within the DAW - meaning you could process your Motif XS with VST Effects, you could use FREEZE and even EXPORT AUDIO MIXDOWN.

the minimum requirement for Cubase Pro 8:
Mac OS X Version 10.9/10.10* Windows 7***/Windows 8.x*
* Native 32-bit and 64-bit Cubase version included.
*** Aero mode needs to be activated in Windows 7