My guess is that Traynor/Yorkville have noticed that locally, here in Toronto, you can find an original YBA-1 on Craig's list or Kijiji pretty much any day of the week.
Price ranges from ~ $450 up to as much a $600 if the amp has had significant "upgrades" based on guitarist needs.
So, if the oldies are selling, why not re-issue that amp and take advantage of a market that obviously is already in place.
As the owner of a low serial number YBA-1, I can tell you that the amp sounds good, lots of tubey goodness, but at its max output, is just not enough for a typical live setting. That and the tone controls are somewhat limited in what they will deliver when twisting knobs.
I do hope that Yorkville does well withthis amp... haven't seen one in L&M as of yet....
Yamaha Bass club member 157 - BB1100s, BB605, Aria owner, Yorkville/Traynor member 62, Roscoe LG3000, Pedulla Rapture