If you don't choose the scrip for scrip (shares) rollover option.
To calculate the capital gain for TTS shares.
Your capital proceeds for your original shares are the total of:
the market value of the TAH shares you received at the time of the takeover, and
the money you received (if any).
then subtract the original cost of the TTS shares.
The cost base for TAH shares-
The cost of acquiring the shares in the takeover or merged company is the market value of your original TTS shares at the time you acquire the other shares, reduced by any cash proceeds.
Please refer the worked example on the ATO website
Regards