No,
Assume a impenetrable mountain range cuts the map in two. There is only one pass to cross into the other side, and it is guarded by a heavily defended, large city, with only one access tile in front, and one escape, in the back. Behind the city is a large civilization, and in front, is your civilization. The only way to win is to capture the mountain pass city from the defenders, but with xUPT, you can only field 5 units in the tile directly adjacent to the city, while the city holds 10 strong, heavily promoted defenders, with reinforcements waiting in the mountain pass, should the city fall.