a. can it replace the Canon for a lot of work;
There is no real reason for one or the other. This is shooting under very controlled circumstances and nothing would be published without finessing tonally, in which case I doubt there need be any apparent difference at all at the end of the production line.
The camera interface was very different on the shoot itself. The live view LCD screen does facilitate getting into awkward spots. The native ISO of 200 does lend a bit to depth of field, as does the smaller image magnification.
With the 50mm lens on the Canon and the 35mm lens on the Fuji the focussing on the Fuji was appreciably slower. The Canon Macro 100mm and the Fuji Macro 60mm both can be very slow searching for focus. I dare say that the Canon wins in this regard.
Like many 'rangefinder' cameras the Fuji is less happy on a tripod but then the electronic level makes keeping straight a tad easier. (I can't recall an instance in over 40 years that I did not have a spirit level on a camera when shooting. And, by the way, the level in the iPhone is a splendid addition.)
b. is what you have shot here simply an additional use that might further justify the purchase of a lighter, 'fun' camera more convenient to cart around on non-work occasions?
I have really had a lot of fun with the Fuji and justification isn't all that much of a consideration. Having said that, it is a bit of an extravagance given that I loathe digital and only engage it for commercial pursuits. The Fuji might go to the big Ebay in the sky and the funds upgrade the Canon system. An 85mm and an EOS 5D MkIII would probably prove handier for me after Tuesday's experience. The Live View is the clincher.
Having had the Fuji since before Christmas I haven't actually used it as a walk-around grab camera even once. That is the sort of shooting I use my Linhof Technika for while the Sinar is wheeled out for more serious motifs.
Probably not the sort of answer you were hoping for, but .....