You would need to use a mex routine to get at the pointer. You would then have a bunch of work to do to figure out how to interpret the pointer. Work that would be easier if you used the documented mex class routines.
The only public property directly stored for an impoint object is named Deletable . The information returned by getPosition() on the handle is retrieved by running code: there is no direct position data stored in the struct that represents the object. Instead you have to look in the hidden api property at the getPosition member, which is a function handle, and you would use functions() to find the workspace property of that handle, and the first cell entry in that will be a structure that has a position member. To phrase that another way, the actual position is hidden away as a shared variable that is in the workspace of a function handle that is stored as a member of a hidden struct member of the returned handle. And you would have to duplicate all of that chain in mex because you want to get "directly" at the information.