Production Plants not consumed for creation of new firm.

Ostensibly, Production Plants are how countries and enterprises build new corporations.

So I bought 10 of them in preparation for my enterprise's expansion.

Have since built five new corporations, and still have 10 production plants. This seems to be an obvious bug.

Production plants are supplied by the host country and paid for by your Enterprise.

You can of course now sell the production plants the enterprise bought or wait for a shortage on the market and sell them at that time.