It would depend on what version of TurboTax they are using. 

If they are using TurboTax Desktop, the customer would need to provide you with either their tax return file and/or the PDF archive of their return from their own computers. The PDF will have the completed forms that were submitted to the CRA, while you can use the return file to carry forward information using Profile or QBOA Pro Tax (if it's a personal tax return). 

If they are using TurboTax Online, they would need to provide you with the PDF archive of their returns.