I just did a quick read of this:

http://msdn.microsoft.com/en-gb/library/hh213080.aspx#CreateAddiitListener

However if using 2 static IPs of different subnets and you use the listener name in your connection string, then the client you use should resolve the listener name to the correct IP for that subnet and hence you should be connected to your current primary.

Thats how I read it although I could be wrong.