PORTPROMPT é de fato a substituição do FILE.
De Criando soluções de impressão em arquivo para Windows 8 - Índice de codificação de firmware :
PORTPROMPT is a new port type that performs the functions of FILE but is updated to work with v4 drivers and handle printing to file from apps running in low-rights mode.
Isso levanta a questão sobre o que é um driver v4.
De Driver de impressora V4 - MSDN :
The v4 printer driver model was designed to address known issues with the version 3 driver model, and thus improve the quality of the experience that users have with their printers. [...]
The v4 print driver model is also optimized for several new scenarios including the following:
Metro style scenarios. [...]
Printer sharing. [...]
Ease of driver development. [...]