That seems to track, at least to me.
Before I get in to this, I've not read thru every post there, just skimmed them. So, if I say something already covered, please keep that in mind and be gentle.
Dialogue in "Saga of a Star World" tells us that none of the other battlestars at the Cimtar Peace Conference (Atlantia, Pacifica, Acropolis and Triton) survived. Tigh comes on the bridge and approaches Omega asking for a status report on the other battlestars. Omega looks at Tigh and says "we're the only surviving battlestar" or something along those lines. So, there's how we know that Galactica was the only of those five to survive.
I'd further suggest that not only that, but that the Basestars attacked en masse, destroying any orbiting defenses, such as ships or stations. Remember that one basestar can field something like 300 or 400 Raiders and at least three basestars were orbiting Caprica prior to the attack. There's also the info that came out about Baltar and his lackey's sabotaging the Colonial Defenses. If you have no fore-warning of an attack and the enemy shows up at your doorstep unannounced, you have a Pearl Harbor type situation. So, even if you have a single battlestar on full alert above each of the 12 Colonies and several Cylon Basestars suddenly show up, they'd be overwhelmed and destroyed in a relatively short amount of time.
Imagine of the Cylon's had three battlegroups of 12 basestars set up to attack the defenses of each Colony in a specific order - Group One attacks Arilon, Group Two attacks Gemenon and Group Three attacks Caprica. You've got one, maybe two Battlestars in orbit and on regular patrol status. Here come 12 basestars at your one or two battlestars. The enemy could afford to take heavy losses in fighters and heavy damage to a couple of basestars that move in and pound on you while the others encircle you in all three dimensions and then open up themselves. With the Raiders doing kamikaze runs on a battlestar it'd be over fairly quickly - and then on to the next Colony on the list: Tauron!
