Revo trial doesnt lock the ECU or anything at all of this nature, however it does leave a Revo version of stock on the ECU.
Tuners will struggle to read off the data if the trial data is still installed, however all that needs doing is to flash a stock factory file to the ecu, easy for any competent tuner to do, the factory stock file is readily available free of charge.
BUT, and this is a big one, some tools are designed to only flash small data areas i.e a file in the Ecu is 1024k but the tool only reads/writes 256k of data so misses off an awfull lot so you dont end up with a fully completed write.
The solution is to always do either:
1.take the car back at the end of the trial and ask for the factory file to be re-installed
2. Make sure the tuner is aware of the trial software so they know that they need to flash to stock.
However, some tuners dont make your new tuned software from your original software, they will look online for a cheap/free tuned file that is a close match to your original software and try and flash just the data area over the top of the existing trial software, this results in a dead ECU or an ECU that needs recovering via BDM (background debug mode) on the bench.
If the tuner does make your new tuned map from the trial, they will quickly realise its not stock and wont try to flash anything over the trial, this is something an experienced professional will be able to see and will carry out the rest of the procedure accordingly.
Luckily for the OP he did use an experience professional and the job was completed succesfully