There was a very interesting article in The Wall Street Journal today ("Twinkies?A Defense", 21 Nov 2012) by Holman Jenkins.
In summary, Jenkin's point is that the big problem at Hostess was not the making of baked products (Baker's Union), it was delivery (Teamsters Union): there was a separate delivery system for each kind of product, and drivers were not allowed to load and unload, so there was a separate loader/unloader, et al. Classic featherbedding.
This explains why the Teamsters agreed, while the Bakers balked - it was a good deal for the Teamsters.
Joe Gwinn