There is at least one call to tmpfile() to generate temporary files in the current code, in eZ\Publish\Core\IO\IOService.

This makes it hard to set by configuration the file folder to be used for temp. files (it is probably possible via an env var, but being able to set it via yml would be easier).
Some sysadmins are adamant that apps should not use the systewide shared temp folder, for security.

Using tempnam() is probably a better choice