I found a little more on MLBPC while researching my next blog post.
MLBPC was actually formed in 1966 (slightly earlier than I had believed) as agent for the Owners and in 1968 the Licensing Corporation of America was awarded the right to negotiate on their behalf. For two decades covering 1968-87, the individual teams had some authority to control their own licensing, although I can't quite suss out if that was only in their local markets or nationally. This may partially explain the lack of Astros logos in 1968/69 for both Topps and Fleer (and some other companies too).
More on this in my next post.