I am moving our source code from Vault to TFS, not bothering with the migration or anything, just pulling a get latest in vault and adding it to TFS.
The solution has go
I figured it out, and I found the answer here: MSBuild not running BuildDependsOn tasks from an imported project
The problem (after looking through the Diagnostic verbosity build output) was that the BuildDependsOn setting was getting un-set. My project files each had the import statement
but that statement was at the beginning of the XML tree. Apparently the import for Microsoft.CSharp.targets can interfere with that import and thus the BuildDependsOn.
My solution was to move the nuget.targets import to below the Microsoft.CSharp.targets import. Now everything builds beautifully.