The vast majority of the East German companies didn't survive simply because they had no competitive products, too many employees and no cash.
I'm quite familiar with what happened in 1990, and the common theme is that the West Germans were astonished to discover just how poor the East German economy actually was in practice. There's an example from Frankfurt (Oder) which had a microprocessor factory - it was thought to be quite advanced, but it actually turned out that the factory had been built (at a ruinous cost to the DDR) and then never modernised, which was the exact opposite of what the Western competitors were doing.
The same apparently went for many other DDR products - for instance, vacuum cleaners from the DDR in the 1970's were on a par with BRD ones and apparently quite popular in the West for the combination of low price and reliable technology. But later on, the Western products improved, while the Eastern products stayed exactly the same - so people simply stopped buying the East German product.
Ironside has never explained where the capital would come from to modernise all the industries that existed in Poland in 1989 without the safety blanket of Comecon. No-one was going to lend Poland money to build original products in 1990 as the real state of the economy was known - hence why many successful Polish companies today got their start by obtaining licences to build copies of Western products. The well known success story Solaris started by building copies of Neoplan buses - and the profits were used to build their own products later.
It's the same story with the shipyards. PiS voters seem to think that the shipyards are viable as public businesses, yet the direct experience shows that the public shipyards relied on subsidised steel - which in turn relied on subsidised iron ore imports from Ukraine. Once the subsidised imports ceased, the shipyards were always going to require heavy restructuring to adopt to a market economy. That's why private shipyards still exist and are doing well, while the public ones went to hell.