hi,

One can take out the micro can get the lock bits opened and steal the code.

Exactly! It is why we drop to use T89C51CC01 and switch to AT89C51CC03. The story was that after some power off/on without external power supervisor installed, lock bits reseted and anybody might read flash/eeprom of that chip.
By the way, out tests show that in our case, brown-out failure erases lock bits AND the first 128 bytes of program memory but rest flash still keeps program/data. Sure, we used and use, and will use external power supervisor but for security reason you mentioned, we drop usage of that derivative and switch to new one.

Regards,
Oleg