The low note that starts the verse riff is indeed an Eb. If you want to play that on a B-string at 4th position instead of an open (downtuned) E-string, you can, but you'll be doing extra stretching and have to move more quickly.
The patterns of the other riffs/fills also fall in line with a down-tuned E-string (think "boxes" on the fingerboard), so in all, it makes it easier for me to play with the dropped Eb.
That note is being generated by his octaver, the note he's actually playing is an octave up from that. You really need an analogue octaver to get it to sound right.

