I don't think so. I don't have access to WinRunner anymore, so I am going on what I remember from a previous project.
Our application had custom properties associated with controls on the screen (web page). We were only able to see this information when pulling the inner/outer html for the control. I don't think it was an item that was seen from the GUI Spy.
With that said, you can always try the following concept to see if your situation is different.
1) Open GUI Spy and see if the property is available for use. If it is in GUI Spy then you can always use it in some manner.
2) IF the custom property is there when you spy on the information for the control, then spend the time to see if accessing it through physical descriptions works.
Now, if that works, you can use the information to connect to the object, BUT you aren't going to be able to access the control as you would any other object since it isn't a standard item to make to a control type. This will mean that you need to redirect all your GUI map information to another method in your scripts. This is a big negative I would assume for you as it would increase maintenance exponentially, and cause a slowing of coding new scripts depending on how your framework has been defined (if you are using R/P, then it will completely eliminate that ability)