In the "Light of Terra" section on page 82, table 2-2 (archeotech treasure table) there is an item "Consort Honor Blade".

It states that it is to be treated as a "Two Handed Power Axe (see page 131 in Rogue Trader Rulebook )" with an integrated hell pistol.

In the rulebook there is NO "Two Handed Power Axe".

There is an Omnissah Axe (2d10+4 p6, power field, unbalanced, seems to be two handed), a power axe (1d10+7 p7, power field, unbalanced, seems to be one handed), and a "Great Weapon" (2d10 p0), to which I could add the "Power" profile.

Any ideas on how this weapon is supposed to be treated?

The power axe described in RT states it has a shorter haft but it seems like it's probably a 2 hander to me. The Omnissiah axe has very similar average damage but a considerably higher max damage. I'd probably go with the Omnissiah axe myself. Also you say 'hell pistol' but the book says 'hellgun' just so you're putting the Basic weapon rather than Pistol weapon into it. It's a pretty nice bit of kit!

There is a new pattern of power axe found in Into the Storm which is noted as being two-handed.

Just found the way I read what you quoted, its just my belief its just a Power Axe that is wielded in 2 hands, doesn't really need any extra special stats of its own really.

Take a Power Axe.

Make it two-handed rather than 1-handed.

Stick a hell pistol on it.

Call it a consort honour blade.