So let's look at the image above and see what they are equipped with. First, you will note that these are painted as Imperial Fists, which is interesting because the IF have always been known as siege specialists to rival the traitor Iron Warriors (in fact, the two chapters had a bit of a tiff a few years ago...). This is a cool choice because of what the centurions are armed with.
All three models are armed with dual assault drills, which first made their appearance as a dreadnought close combat weapon from Forge Worlds years ago. So what do they do? Assault drills (as far as I know) are x2 Str and roll 2d6 for armor penetration against buildings. If they penetrate, they are allowed to make an immediate heavy flamer attack against the occupants within the building.
This will likely change some for 6th edition 40k. First, these assault drills DO have a flamer attached to them. You can see the promethian fuel tanks hanging down in some of the drills and the barrels of the flamer attached to the outside. I don't believe these are heavy flamers, due to the small size.
Something to consider, I think that the assault drills will also get the same advantage versus vehicles. Honestly, how many players use buildings and structured fortifications that GW would feel the need to make a specialized unit to counter them? So in that sense, I think the assault drills will count like chain-fists and have Armorbane as a special rule.
What else are they equipped with? On their torsos, two of the models have what look like assault launchers from the Ironclad Dreadnought (assault and defensive grenades). While the centurion at the top has 6 barrels which looks like a hurricane bolter. So let's add that all up:
- Two assault drills
- Twin-linked flamers (possibly heavy flamers, but it doesn't look like it)
- Assault launchers (assault and defensive grenades)
- Optional hurricane bolters
- Basic marines stats - these guys aren't Veterans, just heavily equipped.
- 2 wounds
- 3+ armor with a 5+ invulnerable
- possibly a 2+ armor with 5+ invulnerable with increased point cost