Page.onPageAttached() never gets called in 1.5?

[Robin Shine]

Hi All, 
We rely on this method to store the page instance being processed into a thread 
local so that we can easily get current page even from component constructors. 
In 1.4 this method is invoked after page is retrieved from session store for 
example when click an ajax link on the page. However in 1.5 it never gets 
called. Is this expected behavior or should I go ahead to create a bug? 
ThanksRobin