I am doing the same thing, but I zip the tile directories, and use that as a source for MOBAC. For example:
<localTileZip>
<name>Sweden</name>
<zipFile>osm05.zip</zipFile>
<zipFile>osm06.zip</zipFile>
<zipFile>osm07.zip</zipFile>
<zipFile>osm08.zip</zipFile>
<zipFile>osm09.zip</zipFile>
<backgroundColor>#000000</backgroundColor>
</localTileZip>
One zip file for each zoom level. The atlas creation with MOBAC seems much faster like this than downloading them via a webserver.
The tile directories are created by the mapnik generate_tiles.py script.
-peter