actually there is no service you need to enable. As the Pearl supports a lot of Bluetooth profiles you just need to pair your Bluetooth GPS receiver with your Pearl and start the GPS application. Every Bluetooth GPS receiver uses the Serial Port Profile
(Bluetooth profile - Wikipedia, the free encyclopedia
) for transferring data over Bluetooth. So you can check whether this is allowed by your IT policy or not. I am not sure if the support of several profiles is adjustable by a BES. It would be great if you come back to me if you know more on this.
Some time ago I wrote an article on "BlackBerry and GPS"
which might be interesting for you. It does not cover the concrete Bluetooth GPS pairing process but it gives you an overview of what is possible if you want to use GPS features on your BlackBerry.