Your presenter catches the click-event and traverses the togglebuttons. It sets each one to isDown(false) except for the one that has been clicked. Try to identify the one clicked togglebutton out of the six possible. In before-JavaScript-times I did this by giving each toggleButton a unique identifier like "button_1". That should not break your MVP-pattern by any means.
Regarding the automatic border: thats a matter of CSS. There a several states you would have to define css for, like .gwt-ToggleButton-down,.gwt-ToggleButton-down-hovering,.gwt-ToggleButton-down-disabled
and so on.