Maybe this article will help.
You need to have the Track-DT drive something that provides feedback. The BD20 is the same way, it doesn't magically provide input to JMRI, it simply detects a train in the block, same as the Track-DT. If you only have a few blocks, with NCE you can use an AUI01 to feed all the Track-DT detection outputs into the cab bus where JMRI can read it. With Digitrax you can use the inputs on a DS64 or SE8C to read the block status and put it on Loconet where JMRI can see it. Either way, you need to add one more piece of hardware to get the detection status to JMRI.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
In pre-DCC days I set up a signal detection system using Dallee Electronics Trak-DTs. Their basic operation is similar to DCC block detectors using an induction coil, but all they do is trip a relay for an analog signal. I could go ahead and replace them with DCC detectors, but I'm wondering if there's a cheaper way to translate the analog (12V DC) signal from the Trak-DT to something JMRI can read. (i.e., an NCE BD20 is $11.99 at a well-known source, would like to spend less if possible).