Verizon has never sold the 6416 (or any of their other STBs).
So anything listed on eBay or any other site is stolen or otherwise not obtained properly (some claim they are found when left behind by previous tenants).
You wouldn't want a 6416 even if it was allowed. Those channels in mpeg4 will not be viewable.
None of the Verizon STB were ever SOLD. You can however use certain TIVO boxes and some other solutions(such as some computer cards). Note that you will still need to rent a cablecard with these devices to get all your programming. As mentioned before make sure you get one that supports mpeg4 to make sure you can get those channels that are so encoded.