I think Bové didn't accept the conditions he would have had to for Buffet to get the Party to agree. As for Arlette, afaik there was never any question of her being the single candidate. She announced long before anyone else that she was LO's candidate and that was that.
I expect Buffet will go ahead rather than break the apparatus. Besancenot... Suppose he can't get his signatures and Bové can't get his either... There'd surely be support at the LCR for pooling sigs on Bové's name...
Probably will do so in future if you don't first, but only if anything changes. All the polling numbers are pretty low for hte LO, PCF and LCR, we'll see what Bove's entry does but my guess is not much. Fai de bčn a Bertrand, te lou rendra en cagant