Since you have mentioned BellSouth I am assuming you are looking in the Southeastern US. If you are located in Florida... I highly recommend checking with Florida Power and Light. Last time I needed some dark fiber, they had the most and at a good price.
You can also try AboveNet, and some of the other backbone providers. They always have dark fiber as reserve capacity and some are even willing to part with it.
I am in SE. Side effect is I am in TN, and Bellsouth doesnt like to play well with others here. LOL The state lets them get away with more then most state does, so I kinda have to play by their rules. :-(
Right now we are just researching, let me repeat researching opening a small DC outside of Nashville (150 - 300 Racks). There are several excellent properties around the area, that meet things like, Power, Not in Flood Zone, Structural sound building, ability to add generators, and HVAC to the site.
The problem is this. I call Bellsouth with the addresses, and they basically tell me unless I am ready to setup an account and place the order, they can not tell me if Fiber is available or not. They say they have to an active order before they will send a tech to the location to see the feasibility of getting Fiber into the building.
I just dont know what to do. I dont really even want to use Bellsouth as a backbone, but they are kinda making it hard to even make the decision if this is feasiable..
Try and find a CLEC in your area, and ask them where the Local Exchange is. Most of the time it will be the ILEC's CO, but sometimes, as is the case with the town I live in, it isn't. It is a tiny building next to the train tracks in town. It is nothing more than a hole in the wall and all the major players (in this area) have equipment racked in there (22" telco racks, and you have to be a CLEC to get access to it).
We have dark fiber coming in from Atlanta that terminates there and then we are running single mode fiber from that location to the DC (all ethernet).
Don't let BellSouth strong arm you, start looking around and trying to find a CLEC in your area that you can start working with. Also try the larger ISPs in your area. They can give you a good idea of where the fiber is in town as well. Find out who owns the power poles, and find out pricing to rent space on the poles. You might also want to check with ITC Deltacom, they are a pretty decent regional player, and I know they are in Nashville. Looking at their network map (http://www.itcdeltacom.com/fiberoptic_network.asp) they have a stright fiber run from Atlanta to Nashville. Might be something else to look into as well.
While I feel your pain with regards to the PSC and ILECs (especially the really big ones with a powerful lobby), I use to work at a CLEC that had to deal with Century Tel, they make BellSouth look like angels.