Run any of the regression tests mentioned below on Ubuntu 15.10 (newest to date, and for a week more). The icon created is black just like the toolbar so you may want either to change color setting rgb to the icon image or better change Unity style.

In any case, it seems that no events go and no action may be forced out of that icon.

It works perfectly well on my 14.04 Xfce4.

RULE "java/awt/TrayIcon/ActionCommand/ActionCommand.java" Exception java.lang.RuntimeException: FAIL: ActionEvent not triggered when TrayIcon is double clicked
RULE "java/awt/TrayIcon/ActionEventMask/ActionEventMask.java" Exception java.lang.RuntimeException: FAIL: AWTEventListener not notified when TrayIcon is double clicked
RULE "java/awt/TrayIcon/ActionEventTest/ActionEventTest.java" StatusError No action after ...uild
RULE "java/awt/TrayIcon/ModalityTest/ModalityTest.java" Exception java.lang.RuntimeException: FAIL: ActionEvent not triggered when TrayIcon is double clicked
RULE "java/awt/TrayIcon/MouseEventMask/MouseEventMaskTest.java" Exception java.lang.RuntimeException: FAIL: AWTEventListener not notified when BUTTON1 pressed on TrayIcon
RULE "java/awt/TrayIcon/MouseMovedTest/MouseMovedTest.java" Exception java.lang.RuntimeException: Mouse moved action did not trigger
RULE "java/awt/TrayIcon/SecurityCheck/FunctionalityCheck/FunctionalityCheck.java" Exception java.lang.RuntimeException: FAIL: ActionEvent not triggered when TrayIcon is double clicked
RULE "java/awt/TrayIcon/TrayIconEventModifiers/TrayIconEventModifiersTest.java" Exception java.lang.RuntimeException: FAIL: mousePressed not triggered when SHIFT + BUTTON1 pressed
RULE "java/awt/TrayIcon/TrayIconEvents/TrayIconEventsTest.java" Exception java.lang.RuntimeException: FAIL: ActionEvent not triggered when TrayIcon is double clicked
RULE "java/awt/TrayIcon/TrayIconMouseTest/TrayIconMouseTest.java" Exception java.lang.RuntimeException: FAIL: ActionEvent not triggered when BUTTON1 is double clicked
RULE "java/awt/TrayIcon/TrayIconPopup/TrayIconPopupTest.java" Timeout none