What does bringing another contractor into this mean?

Here's a quick description of the situation as it stands right now:

Government Organization 'A' hires contractor 'B' to provide IT services. 'B' hired a placement agency 'C' to find someone to do occasional (once a quarter or so) IT work in support of that contract. 'C' put an add out on Monster, and I answered it, and eventually got the job. Now 'C' gets a cut from every one of my pay checks.

It's gone on for 6 months or so, and everyone at 'A' and 'B' is very satisfied with my performance. So much so, that they want me to do 'regular part time', which would mean about 20 hours a week of after-hours work, either on the weekdays or weekends. That hasn't been nailed down yet, and will be discussed at a meeting today at lunch.

The owner of company 'B' sends out an email announcing the meeting. He sends the email to several people, as well as saying who is going to attend. He mentions himself, me, the other guy that works for 'B' providing servicese to 'A', the guy at 'A' that oversees the contract, and some lady I've never heard of who's email address is @ contracting company 'D', which I've also never heard of. Internet research says she owns company 'D'. To my knowledge 'C' knows nothing about this.

My question is this. wtf does that mean? I mean, the meeting is today, so I'll know soon enough anyway, but i'm still curious if anyone can offer any perspetive.