There is no Universal Saftey Insitute where they test crash Galaxis , and we have no idea if the indivual stars in a galactic collision will line up such as there mutual gravitational atractions leads to head on collisions. Both galaxis are rotating and presumably there are sections ,unknown and unknowable, that will interact much like gears meching, where the chances of collision are much higher over time. Reducing the whole thing to a simple probability of something like two fields of dots, pushed strait through each other may not be valid, and I am absolutly cetain that no one has the compute needed to run a simulation on billions of varied gravitational singularities moving and interacting with another set......... which is of course all my lead up to do a pitch for a mega intraferametric space telescope to observe actual coliding galaxies and other phenominon, to be built sooner, rather that later. would also be good for looking at details on exo planets.....give it a realy wide focul length and it could also zoom in on asteroids and comets for research, early warning of impacts and determining potential space mining candidates. current work in space navigation is focused on providing ultra high precision data links between different satelite units in an array that will alow introfermetry to work without a physical conection between the sensors, making for larger, cheaper telescopes, that are orders of magnitude more powerfull than anything built yet