I am going on memory, since I sold my Piston bindings recently....
Theoretically, yes, but I think there will be a height mismatch unless you got a whole new riser plate. The heel piece screws directly on the ski through a piston-specific riser plate, which is height-matched (and mates up to) the front toe piece. The toe piece does not have a riser, but rather, slides into a guide track (the guide is what's screwed into the ski up front). That guide gives the vertical "rise" to the toe piece.
Theoretically, you could separate the toe piece from it's sliding mount to have a basic Marker toe piece, sans riser. If you could find proper riser plates front and rear, then you could probably screw the bindings directly to a ski, without the piston getup. But I am sure that would be a heck of a project finding all the parts and making it work. Oh, and you will need new screws too, since the screws that come with the piston mount are probably not the right length for a flat mount.
Why don't you just remount the bindings, piston and all? Or are you going to an application where you need a flat mount with no rise?