It all looks a bit Orwellian, no? Scary stuff.
Sorry for the long radio silence. Work has been a tad busy in the last few weeks (which is poor timing, considering we're right in the heart of grad interview/recruitment season).
Anyway, I noted there've been a fair number of questions on the topic of second round interviews, and the formats in general.
In terms of the first round format, it's pretty straightforward, typically (which is always nice). There will typically be an interview with account handling and planning. Sometimes, it's broken into two - so you have the account handler ask you the more practical questions, and the planner talk about the theoretical, but it's almost always a variation on this theme.
To the first of the questions in the last post's comments - the sort of questions an account handler might ask, v.s. a planner. Typically, a lot of agencies have a good cop/bad cop approach, and it's USUALLY (though your mileage may vary) the account handler as the bad guy and the planner as the nice chap. I have had this be different. The account handler will ask you about why you think you're relevant for advertising, what you'd do in a series of hypothetical situations...those sorts of more robust, practical notions (yes, even teamwork questions on occasion, given the job)
Basically, he/she is thinking about whether you can get shit done. The planner will tend to focus on what you think the thinking is behind a series of ads/whether you know the difference between an execution/campaign, and what you think makes a good one and why. They may even talk about ad theory/what's going on in the business today, and you should be prepared for that.
In terms of a video interview, I have to say, I've never ever had one (have any readers?), but I think on video (based on a fair few tele-conferences I've had), it's even more critical to be clear, succinct and to the point. You lose out with people not being able to note your body language so easily - so preparation is perhaps even more key.
When it comes to JWT, they have a very clearly defined mission and strategic approach. Explore the writings of Steven King, have a point of view on good global campaigns, and I would imagine (with a healthy nose at the key people at the organisation and their twitter/sites/the main site), you'll be in good shape. I wouldn't like to guess at the culture, because I've never worked there. If anyone from JWT is reading this, feel free to chime in.
Finally, in terms of two separate interviews - yes, there is typically some overlap, but given it'll probably be two different types of people, with two different job roles interviewing you, so naturally, even if the questions are similar, they'll be looking for slightly different things. Think about a planner - they are absorbed by the theoretical, and how it can live in the real world. They'll naturally tolerate more theoretical musings than an account handler, who has to make sure shit gets done. So don't be surprised if you come away from any ad/comms interview thinking that you made a better impression on one than the other.
I hope that little lot's helpful. There are a few more agency grad schemes that I've forgotten, and will put up shortly.