More details have emerged from investigating the captured Fateh Al Islam members.  This from Annahar today:

Translation (mine):

As the rounding up of suspects in Tripoli intensified, Annahar obtained insider information from the investigations. “The Fateh Al Islam scheme was comparable to a ‘Lebanese September 11′ in its scope. It involves destroying a large hotel in Beirut in addition to bombing Shikka tunnels.”

But the most significant bit was this last sentence:

The explosives they were planning to use arrived to Lebanon via Syria. They were found in a warehouse in Tripoli.