I have four projects in my Visual Studio solution (everyone targeting .NET 3.5) - for my problem only these two are important:
Using deadlydog's scheme,
Y => X => A => B,
my problem was when I built Y, the assemblies (A and B, all 15 of them) from X were not showing up in Y's bin folder.
I got it resolved by removing the reference X from Y, save, build, then re-add X reference (a project reference), and save, build, and A and B started showing up in Y's bin folder.