there’s a onIconize callback function where you can pass whatever you need; it get one argument (o) rapresenting the referred container.

$('#myContainerID').buildContainers({
   ...,
   onIconize:function(o){
      o.mb_changeContainerContent('yourContent.url',"dataToBePassed");
   },
   ...
});

If you have more than one container on your page but you need to add the event to a specific one you should init this separately:

$('#myContainerID').buildContainers({
   ...,
   onIconize:function(o){
      o.mb_changeContainerContent('yourContent.url',"dataToBePassed");
   },
   ...
   });
$(".mbContainer").buildContainers({
   ...,
   ...,
   ...
});

Even if your container has the same class of the others it will be skipped by the second initialization. Otherwise you can add your own custom class to initialize each specific containers (doesn’t need to use “mbContainer”).