Im going to give the enemy support who owned this fire-base benefit of the doubt and he was not hacking. So if this is a glitch please uber hunt down the cause and violate it. I have dealt with this a number of times and interestingly enough twice by the same support from the video. God i hope this is not a hack. You can see in the vid both me and the enemy support have good ping to the server. The fire-base in question starts 50 seconds into the video. http://www.youtube.com/watch?v=E86QFLCf6xE
Re: Invicible Fire-Bases (video) its a common bug it can happen to all classes i believe but i usually encounter it with tank while using the jet gun if you had changed to rail gun you would have had no trouble shooting it