Joseph- that is incorrect. The halacha is that a man shouldn’t walk behind a woman, not that he shouldn’t be behind one. There is a huge difference between the two. I see men (including very chashuva men) sitting behind women on city busses all the time.
Personally I feel that if a company wants separate seating they should either do side by side (like on the Monsey bus) or do women in the front. This way a pregnant woman who is easily nauseated isn’t subjected to the additional bouncing of the seat from sitting in the back.