I have similar problem with My Subaru Tribeca 2009 and Fortin starter as it start randomly the car without any humain intervention. At first I change the batteries on the two FOB but it continue to do it randomly. I decide to remove the battery on both FOB and to my suprise the car start again on the same day?!
Did you find anything on your issue?
I believe I have a FSA starter, will try to find the model tomorrow. The FOB is grey black with 5 buttons. Is there any recall or know issue of the starter to this behavior? Seem like a bad contact as it never did this before and I own the car for 5 years now. The stater was install the same time I took ownership of the car.