I have listened again, and I still think the rhythm guitar stays on that A7(Your B7) but the bass player walks up by half steps, so you could play:

|B7B7/CdimCdim/C#m7C#m7/E7E7|

to get the full bass effect, you'd do it like this:

*B7* 7-x-7-8-x-x

*Cdim* 8-x-7-8-x-x

*C#m7* 9-x-9-9-x-x

*E7* 12-x-12-13-x-x

I think the Cdim probably should be called B# dim in this instance, but I'd have to think about it to be sure--

Still haven't figured out which recording you are listening to, but mine is great--a tight, punchy Western Swing arrangement with horns, steel, and accordion--I'd have loved to play with that band!!