Not many I can think of.  Mostly very short single scenes if anything is mentioned at all.  You can rub Sasha's ex's nose in your potential relationship.  But he is a definite ex at that point.  If you pursue Amy, her boss is interested in her, but she's decidedly not interested in him. 
Samantha gets engaged/married and you can get involved with her, but most of the paths aren't netorase.  There is one path where the husband confronts you but Sam has effectively already dumped him.  Most of that action is her revenge cheating / grabbing onto a safe guy as her relationship implodes.
Aletta and Cherie come closest.  Aletta is your boss and is fucking her boss, Dwayne, and you can get involved with her.  Dwayne never notices.  Cherie is married to the same guy and you can entice her to help you, but there aren't any real romantic/sexual scenes yet -- she's a focus of an upcoming DLC.  Dwayne does come and tell you to back off once.