As far as I understand it, yes.  It would not only left click but hit what ever button you had programmed such as "1" for P1 start.
Sorry, had a brain fart.  In Mame, you can assign mouse buttons as keys, so in effect you would not wire your mouse buttons to the keywiz.  Sorry about that, it's been a long time.  I had two buttons on the side of my first cp.  One was a mouse button, the other was a button for vpinball.  That's why I was a little lost there.