Well I got a hold of the previous owner and he had no idea what I was talking about. He said he used the OnStar system. Must just be that the owner prior to 2009 put the antenna on to increase the range of his cell phone. We'll leave it at that and thanks to all that offered help.
Not sure what happen to my last post but here goes. I found the previous owner and contacted them. They only used OnStar since 2009 to present and they didn't know anything about the antenna on the upper right side windshield. The owner prior to 2009 must of had it installed and I assume that at that time there was no such Onstar conversion kit available. So we will just leave it that the antenna was a range extension for a cell phone before 2009. Thanks to all for all the info.
Not sure which you're talking about. The antenna on the OPs windshield enhances CELL PHONE signal.
Click on the link I posted for a description of BlueStar
To check to see if it's working, you would have to go to a location with poor cell phone coverage. With the car turned off, check to see how many bars is on the phone, then turn the car on and recheck the bars. If you see an improvement, then it's still working.