IIRC We played that it was effectively a new company.
The rules as written imply that the insolvency marker should be retained by he bankrupt company, and from that POV this should be the official interpretation. I'm guessing this is a popular approach.
However this was not the original intention - the idea was that the only difference between a new company and a refloated one was that the refloated company retained any trains/cash/tokens that it had before. In practice this meant that it did not retain the position of being insolvent as it was effectively a "new" company.
I have no problems with the either approach, and it is worth noting that keeping the insolvency marker does make the refloated company even more powerful than it would be otherwise, and they can be pretty powerful things. Since this is how things are in the rules, I would suggest the literal approach should probably be the "official" interpretation, with the original intention being a possible variant (with agreement of all the players).
Sorry for not covering this adequately in the rules.