I work in automotive software, and PowerPC CPUs (albeit from Freescale and STMicroelectronics, not IBM) are more popular than ever. It's a very common choice for powertrain ECUs.
Power Architecture is used in spacecrafts as well:
The [PowerPC] 603e processors also power all 66 satellites in the Iridium satellite phone fleet. The satellites each contain seven Motorola/Freescale PowerPC 603e processors running at roughly 200 MHz each.[1]
There is a radiation hardened version called "RHPPC" based on PowerPC 603e made by Honeywell & Freescale. RHPPC is equivalent to the commercial PowerPC 603e processor with the minor exceptions of the phase locked loop (PLL) and the processor version register (PVR). [2]
The F-22 uses PowerPC processors in the upgraded Common Integrated Processor(CIP) avionics, partly for compatibility with the F-35 Integrated Core Processor (ICP) avionics.
F/A-18s also use PowerPC processors in the Advanced Mission Computer (AMC) avionics.
General Motors was a big user of Motorola 68k variants. Workstations and personal computers that used the 680x0 series switched to the Power series, maybe the developers just find them easier to migrate to.
The ISA is not better than others in any real way, but IBM put a lot of early work into RAS features for their server chipsets, and this sort of leaked into the automotive and aviation world.
If you want to run 3 cpus lockstep, verifying each other's results, the PPC world already has the infrastructure. This and other similar things make it an easy choice for some applications.