There's definitely some sort of filter effect heard, maybe it's the varitone, that's as good a theory as I've heard. For awhile I thought it might be a cocked wah or similar. I've read mixed reports even from the man himself about whether it was the ES 355 for TSOR or one of his newer (at the time) modded strats with a hb in the bridge. I've also heard him say flanger much more often, but I've heard him say phaser as well, although I tend to agree it's more flangeresque to my ears. I'm sure it's possible to get close with a phaser given the appropriate signal chain. On the III, the flanger straight into a chorus block gets closer than anything so far, and I've been messing around with pre and post filter blocks but I'm not quite there yet. I agree that he's never replicated the recording sound live, it's usually not anywhere close.