First, as you likely know, the old portals won't work in the new game. Duh.
But... they do work!

As in the older games, you cannot connect multiple portals to the same system - it displays an error message that there are too many portals connected. Oddly, this error message is quite similar to the old one and even shows the wireless USB dongles being connected instead of a wired portal (which is all you can use with SWAP Force).
However, using the previously discovered method of setting portals side-by-side, the older portals will read and write figures into the new game - including SWAP figures.
This makes me wonder if the limitation is more of a software than a hardware limitation.
Oddly enough, the 3DS portal sitting next to the console portal doesn't seem to work for daisy chaining. If I set the 3DS portal on top of the console portal, but have them overlapping just a bit (think MasterCard logo), then put the figure on the part of the 3DS portal that isn't overlapping, the console portal will then read the figure - even with the 3DS portal powered up! This is interesting, as before, if the second portal was powered up, it would interfere with the first portal's ability to read the figure.
Just some neat things.