How to connect a Bamboo remote agent from within Intranet
So I am assuming that

1) you have a PC on your LAN.  The PC can only talk to port 80 outgoing via a proxy

2) you have a bamboo server running a cloud service

3) you wish to initiate a connection from the bamboo server to the PC

Don't get your hopes up but this answer https://stackoverflow.com/questions/19161960/connect-with-ssh-through-a-proxy

explains how to use a http proxy to tunnel ssh.  Unfortunately most http proxies disallow the CONNECT method

Once you have the ssh to the remote cloud service set up then try it again 
with a -R option to allow a reverse tunnel

Then you should be able to connect via the reverse tunnel back to the Lan PC