Is it possible to fight legate lanius before the final mission?

I don't think it's even possible to meet him.

There's no way to go to his camp until the final battle.

I'm on PC so I TCLd through the gates on the dam and went to his camp early one playthgouh. You can kill all the guards and do everything just like in the end quest, but his tent says "Locked from the inside". So I activated it by console and went inside. I was villified by CL so they immediately attacked me and Lanius was set essential. We bashed each other around for a good 10 minutes until I got bored and loaded a different save. I haven't tried this with my CL character to see if you get any dialog options if they're not hostile. Maybe I'll fire up that save and see what happens.

-Gunny over.

Update:

I just went to the compound with a character idolized by the CL and while all the guards outside were friendly, after I console activated my way into the Legate's tent, he immdiately entered the dialog tree as if I were an NCR champion there to challenge him during the NCR end scene. Oh, and he's still set essential so mashing him around with Oh Baby! again got boring.

-Gunny out.