I'm having difficulty finding it, but on slashdot (i believe) and other
news sites within the last couple months there were pointers to an
article by a guy in like eastern WA that set up his own site to site
broadband over "clean dry pairs" from his local phone company. He even
named a couple modem brands he was using and mentioned that over a 15
mile or so wire length, he was getting half-t1 speeds.  Maybe this is
what you're trying to do over the existing bldg-to-bldg phone lines?

....

Found it!!! "The SDSL Homebrew Home Page.
http://www.odessaoffice.com/sdsl.htm

"Kimi A. Adams" wrote:
> 
> The reason that I am running or attempting to run connectivity to T-1 is
> because DSL is maxed out here.  The owner wanted another solution, which we
> have but the cabling is too old to work with.  It's not 100 pair CAT 5
> apparently.