Good comments Torben.
The slide you have linked to talks about Mason's autohandler and dhandler functionality and parallel component trees.
dhandlers are basically equivalent oacs .vuh files
autohandlers are equivalent to our templating tree (master includes child etc.) except the other way around - inheritence is implicit and you need to flag if you want to ignore it for a particular file rather than request it (as oacs does with the <master> tag).
The parallel component trees is quite a nice feature. You can include a component (ie. a small include chunk) with relative or absolute paths as you would expect. But you can configure multiple component roots. One will always bee your www doc root, but you can have other library roots.
So if you do this to include two components:
<& /foo/bar.comp optional arguments... &>
<& /themes/client1.comp optional args... &>
Then these multiple file paths can be searched on your disk in orderl (like how a compiler searches for include files for example).
This means that in the example above, the theme include could be shifted to an nfs volume without having to change any of the rest of the file organisation or site coding.
Other than this multiplpe path searching, it's exactly the same as oacs includes.
