Reading about this sonic thing; I've came to another excellent thread: http://forum.cockos.com/showthread.php?t=91439 Bottom line, it's about a reversed engineered version of a BBE 482i; so you get a little bit more insight on what the BBE process does. Liteon (a Reaper user that already have a bunch of fx into vanilla Reaper) actually did a great implementation of this effect in JSFX.
I've liked it so much that I have made a "personal" VST multi platform version. Also come with a fugly interface with "wood pattern"; just like the plugins in the 90's. The knobs are by AZ.
The code is also fugly (the plugin wrapper) but the DSP algorithm of Liteon is pretty impressive. Try it !
Source Windows OS X