If you’re like me you absolutely loathe the issues that Maya causes when it adds the ‘opposite’ node if you scale a mesh in the negative (in order to mirror it, because frankly some of maya’s default mirroring tools are a bit meh).
I made a script a while back that’s a sort of “advanced Maya Mirror” with a few extra options for where you can set the mirror axis, what happens to the original and new mesh copy, even auto-reversing normals for the mirrored object (and best of all, not opposite nodes applied!)
http://www.creativecrash.com/maya/script/advanced-maya-mirror-tool
Enjoy!