
This also happens in 6.6.01 Beta Version.
The exploit works on both government firms and AI firms, the example below shows the government firm version and lets you transfer any AI firm to yours at market value.
Step 1 -
Go into Corporate Details
Highlight Any firm (except the firm you want to receive the AI/Govt firms)
Click Transfer Firms Button
I haven't found any way to actually select which firms you want in this screen its either select all or none.. ( You can use the filters to select a group of buildings by type/corp/city etc ) but beware if you select some, the deselect option doesn't work, so you have to start again if you don't want to include those you selected.
Step 2 -
Click Select all
Click Transfer
Choose the firm you want to transfer the firms too and press ok
After doing this on Commercial buildings and Media Buildings too, you can see from the images below, the government no longer has any firms and i have a lot.
In a separate test i was able to transfer all the telecoms buildings from the telecoms company to my own.