Let's consider some test application: when I'm trying to deploy it, everything is going right way:

dmitry.ginzburg@oracle-ginzburg:/local/work/packagerTestsSuite/apps/HelloWorld$ ls dist
HelloWorld.jar
dmitry.ginzburg@oracle-ginzburg:/local/work/packagerTestsSuite/apps/HelloWorld$ javafxpackager -deploy -srcdir dist -width 100 -height 100 -outdir dist -outfile HelloWorld -name HelloWorld -appclass helloworld.HelloWorld -title HelloWorld -vendor Oracle
dmitry.ginzburg@oracle-ginzburg:/local/work/packagerTestsSuite/apps/HelloWorld$ ls dist
HelloWorld.html HelloWorld.jar HelloWorld.jnlp

Now let's try use -callback option:

dmitry.ginzburg@oracle-ginzburg:/local/work/packagerTestsSuite/apps/HelloWorld$ ls dist
HelloWorld.jar
dmitry.ginzburg@oracle-ginzburg:/local/work/packagerTestsSuite/apps/HelloWorld$ javafxpackager -deploy -srcdir dist -width 100 -height 100 -outdir dist -outfile HelloWorld -name HelloWorld -appclass helloworld.HelloWorld -title HelloWorld -vendor Oracle -callbacks onJavascriptReady:alert \(\'Hello\'\)
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/tools/ant/types/DataType
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at com.sun.javafx.tools.packager.Main.parseCallbacks(Main.java:168)
at com.sun.javafx.tools.packager.Main.main(Main.java:275)
Caused by: java.lang.ClassNotFoundException: org.apache.tools.ant.types.DataType
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
... 14 more

That's what we see. So, the whole option is not working.

I attach the project: to see the result you should use that command:
ant -f simple-build-big-cli.xml deploy-with-callbacks