Blackberries have, like everything else, been made in China for a long time. Their trick is for the OS to be able to cryptographically verify parts of the hardware and boot loader sequencing. The OS (certainly their classic OSes BB10) would refuse to run if it didn't like what it saw.
That's what set Blackberry apart in the eyes of government users; they'd thought about checking the integrity of the hardware and firmware. A bit like a PC's Secure Boot today, but for a phone. It makes tampering very difficult.