Starting with version 1.1.4, it is possible to generate all the syntax diagram of a particular grammar without having to use ANTLRWorks GUI (which make it possible to include into an automated process). To do that, use the Console of ANTLRWorks.
$ java -cp antlrworks-1.1.4.jar org.antlr.works.Console
$ java -cp antlrworks-1.1.4.jar org.antlr.works.Console -f test.g -o output/ -sd eps -verbose