Does anyone know if when I have my BB tethered to my laptop if it is visible on my BES?

You should always assume everything is visible over your BES.

Tethering does NOT go through a BES server. With that said, tethering is as safe as any other web browsing.

Yes, tethering should be safe. I am not sure about over the BES but logical sense will tell me that since you transferring data though your cell phone and not your company network, you should be ok.

OT, if you use a wireless laptop to use some of the Hotspots, that's when you may not be safe at all. Never use a wireless laptop to transfer sensitive data using Hotspots.