The solution that was eventually implemented was to use a wrapper for the callback function of the Ajax call and in this wrapper check for the existence of a specific element on the returned HTML chunk. If the element was found then the wrapper executed a redirection. If not, the wrapper forwarded the call to the actual callback function.
For example, our wrapper function was something like:
function cbWrapper(data, funct){
if($("#myForm", data).length > 0)
top.location.href="login.htm";//redirection
else
funct(data);
}
Then, when making the Ajax call we used something like:
$.post("myAjaxHandler",
{
param1: foo,
param2: bar
},
function(data){
cbWrapper(data, myActualCB);
},
"html"
);
This worked for us because all Ajax calls always returned HTML inside a DIV element that we use to replace a piece of the page. Also, we only needed to redirect to the login page.