What Nortel is doing is to allow each customer to get their own "channel" or (to be more precise - lambda) without their data interfering with the shared customers.

Let us assume that you have a fiber line with a data rate of 100Mbs to an office building; currently all of those customers share that bandwidth. Now, install a 40 "channel" WDM PON box at that building, 40 of those tenants each one could have their own 100 Mbs data stream.

Increased bandwith, with just a "box change".

That is what is so special about it.