So....the Carnival of Light...(possible spoilers)

Yes to this one, the others I don't know. She's even able to help keep Mother Mayhem out of people's heads (only to the point where Mother can't tell who or what you are though.)

So far, the only Praetorian Earth Carnie I've seen has been Vanessa. She doesn't look nearly as cool as her Primal Earth counterpart, and she seems to have the very same costume as Primal Earth Carnies.

Actually, I think Posi stated that parts of the old Prae arcs did happen, and that the new updated ones are sort of another stab at invading or something, I guess. But GR isn't pre-any issue.

CoH has an odd sort of continuity. In effect, there are two forms of precedence, intra-character precedence, and extra-character precedence.

Intra-Character Precedence is how your character experiences the world. For your character, the clockworks are thought to all be machines until you help discover otherwise, Nemesis is thought to have disappeared until you discover cronies working in his name, and other such revelations. One character discovering the true nature of the Clockwork doesn't actually inform that contact of this fact after you finish talking to him: the next guy that talks to the contact will result in him being all "find out stuff about dem clockwerks, herp derp." though any missions your character goes through after that period assumes you know this, and that it's common knowledge.

Extra-Character Precedence is stuff which effects all characters at the same time. The Calvin Scott TF was only around for one (a few more?) issues, and heralded the change from Sister Psyche inhabiting Aurora Borealis' body to regaining her own. When the council took over the 5th Column there was a big "event" where huge 5th vs Council battles would rage in the streets. However, a character that levels from 1-50 after that change will have their character always assume this is how it is: Your missions don't go from 5th Column to Council at level 20 with a big story arc.

There are goofs and gaffes, and in-between states here. During the 5th Column to Council change, all mention of the 5th column was wiped from the game, even in a historical sense, turning precedence into a a total retcon (though some of this has been re-retconned back to the original form) Past certain levels it's assumed your character has certain knowledge, even if arcs in which you learned such things have not been experienced (Omega Level Clearance issues nicely bypass this, with statements like "you may or may not know this, but...") What side is Requiem on now, now that the Column is back in action? And when is he on which side?

I haven't run the new arcs yet, but my impressions are that they are a little of both. The mission where you rescue the Praetorian Carnies is a stand-alone mission, not part of a larger arc, so I see no reason why that mission couldn't be entirely Intra-Character, even if the others aren't.

All of the CoH content in general operates on comic book time and is somewhat fluid. You'll notice that aside after the first Rikti invasion in 2002 pretty much no exact dates are given in game.

The obituaries in the villain paper missions all end in 2008. I think that's the newest date we have.

This. I haven't actually done that mission since GR release but I see no reason why it would have to be redone beyond swapping out the old Clockwork for the new ones. The new arcs have nothing to do with it, since the mission isn't part of them.

Although I have heard that Vanessa does show up in Tina MacIntyre's new arc. Confirm? Deny? Details?

If they are "good guys" they should be allied with Cole.

Right, CoL didn't appear in an arc, that was a standalone mission.