Eclipse doesn't provide maven artifacts in general, because most project's rely on OSGi and p2. The Xtext project, which maintains MWE hasn't yet uploaded the jars to any maven repository. You can find a slightly older version here :
https://www.fornax-platform.org/nexus/content/groups/public/org/eclipse/plugins/
Not sure if it works for you, there hasn't been too many updates in MWE2 since then.