Which professional routers? Cisco doesn't use QNX and Juniper uses FreeBSD. I'm not sure there are any other router manufacturers that matter.
Other than on their most expensive, powerful routers.
I've still yet to meet someone who actually prefers Cisco over Juniper MX. I wonder who is buying these?
You have met my ex-boss.He had no reason to necessarily prefer Cisco other than that's all he was accustomed to.
EDIT to add jacquesm's comment:
https://news.ycombinator.com/item?id=14231160
Mine on Lobsters summarizing a lot with links:
https://lobste.rs/s/ensbd6/building_blackberry_qnx_7_desktop...