When my service starts another application, which works with network printers, that app can see only local printers.
And when that app starts independently, it's all right. I found out that it is because of system privileges. And now I can't find out,
mayby it is a feature of the operating system, or bug.
I use a static function QPrinterInfo::availablePrinters(), which doesn't return network printers, when app starts with SYSTEM privileges.

Sorry for my English