quick answer. nope. hicas and attessa are seperate, but use a lot of similar inputs.
To test if the 4wd is actually working, pull the fuse either under the dash, or in the engine bay, find a nice stretch of "private" road and dump and go. Then turn the electrics off, put the fuse back in and rinse and repeat.
I find in the wet if i have it in 2wd it is insanely bad, like driving on wet oil. In 4wd even in very wet conditions I can't get it to spin a wheel.
The other thing you coould do is stick your head in the boot and see if there are any error codes on the attessa module. search for the code list..
james.