Their concerns were misplaced and the outcome lawsuits against the Australian government (they won every time) show how ridiculous the scare campaign about ISDS was.
The TPP would drastically increase the number of nations with reciprocal ISDS agreements. In particular it would have included the US, where many/most of the the tobacco companies are domiciled.
Why the TPP would probably have not included retrospectivity, it could have frustrated any future efforts.
See also the outcome of Phillip Morris v Uruguay