The WAI-ARIA support functionality of the PanelBar will be available from the R3 2016 release which is due mid September. Please excuse us for not specifying that in the article, we will update it as soon as possible.
As for the enabling of the TreeView's WAI-ARIA support you could review the TreeView WAI-ARIA Support
article. Generally, to enable that functionality you should just set the EnableAriaSupport property to "true". In order to use WAI-ARIA the form
element on the page must have a role attribute set to "application" (role="application"). For more information on this requirement see: W3C: WAI-ARIA
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