I've just released the first build of Blackberry Ant Tools project on sourceforge. Blackberry Ant Tools
The project currently contains a rapc task and a sigtool task. Both the rapc task and the sigtool task perform "up to date" checking to conditionally compile/sign only if one or more of the source files are newer than the target file.
The RIM JDE .jdp and .jdw files are not required. All cod file settings are specified in the build file or optionally in a separate properties file (and then imported by the rapc task). Everything you can do with the JDE has been replicated in the rapc task (except the concept of the workspace and dependencies since ant gives you the power to do this in your build file).
The project website has a full reference and a series of examples. Please give the project a try and provide feedback on the sourceforge page.