Should I have gotten annoyed and reported that big boobs black woman to the railway police for sexual assault or should I have just tried to enjoy the ordeal and count my blessings!? 
Sexual assault... in fact any assault has to be intentional (intent to touch in a manner that a reasonable person would find objectionable). It would do people well to try and not belittle what is a serious offense.
Yes Bakes it was intentional, in that she knew what she was doing was wrong but she just did not care!!
Thanks for the advice! If it ever happens again then I will know what to do if I am not enjoying it!! 
Well you were there, so you know what happened. I could also give my own story. In my younger clubbing days (I still young eh, but I have long outgrown the club scene), some drunk females grabbed my buttocks as I was going up to the dance floor with my friends.
It felt strange, but I did not feel violated because I did not feel physically threatened by these women. They were about a foot shorter and at fifty pounds lighter than me.
I agree with Kicker's point regarding the male-female power dynamic. In a situation where the male is the perpetrator, it is more traumatic for the female because there is the added element of physical intimidation involved.
With regards to Dutty, if the woman is your boss, then that changes things completely because the woman has the power to fire you.