I guess there are two matters at hand, one being whether or not Alpha Proxima is in fact located in the nearest star system to Sol, Alpha Centauri. I think several points in the Author's story indicate it isn't, unless there's a neutron star nearby us that we're unaware of, and/or Matt Decker is completely ignorant about our celestial next door neighbors for the last couple centuries.
The other matter pertains to whether or not Alpha Proxima is a Member World in it's own right, as TBatB would seem to show, with its own individual representation on the Federation Council, or whether they are some random colony that's grouped in with several others.
EDIT: And I'm a Johnny-come-lately... What KRAD said.
btw, Just got a Singular Destiny, Yeah Baby! But when's Issue #2 of Farscape coming out?