The answer to your question is: Probably yes.
That question depends on your / your costumer configuration, and the point of view.
The type of tunnel you are using to create the VPN - PPTP or L2TP - also determines the level of security and anonymity of your VPN. (L2TP being more secure)
If you are using your costumer network - whatever its based - and on top of that you are making a VPN between *your* computer and the remote network, that traffic, the traffic tunneled by *your* VPN will be encrypted and not be accessible to everyone.
If you use a remote gateway, from the remote end of your VPN to access the internet, and if all internet traffic you're generating, IM, P2P, etc. is using that (remote) gateway, your traffic is completely shielded by your VPN.
But if, for example, you are browsing the internet, IM, etc. in your laptop, but using the local gateway (that Juniper at your costumers site) to access the internet, that traffic is completely proxied / firewalled by your costumer. It will "see" everything you're doing...