Since Windows RT is a closed platform that does not allow running unsigned desktop applications, acquisition options other than sending the device to the manufacturer (accompanied with a government request) are limited.
Since most Windows RT devices (as well as many tablets running Windows 8/8.1/10) are properly equipped for BitLocker drive encryption, the chance of encountering a device with an encrypted system partition is higher. (To recoup, BitLocker full disk protection is activated automatically by default, without user intervention, if the device is equipped with a TPM module, has non-removable (soldered) RAM, and the user logs in with their Microsoft Account as opposed to using a local Windows account.) More on BitLocker protection in BITLOCKER DEVICE ENCRYPTION. Note that BitLocker Recovery Keys can be obtained from Microsoft with a government request.
BitLocker encryption is volume-based. On eMMC and SSD drives, BitLocker provides trim pass...