Merger after merger after merger followed by a massive adoption of public cloud (using Direct Connect/Express Route for hybrid connectivity) has led at least two very large FinServs I worked for adopting CGNAT (100.64/10) for parts of their internal networks.
In both cases RFC1918 was used throughout their global network and while not fully used, had become highly fragmented over time.
Been around in other cities for as long as I remember. The nearest junction to where I grew up in Glasgow in the 80's allowed crossing in all directions at one time.
On the contrary, many major companies, especially finservs have multicloud strategies to avoid lock-in or concentration risk (a real concern of regulators). Platforms like pcf and K8s allow for (easier) porting between clouds rather than building directly to cloud provider api's.
Their pricing was based on application instances and the list price was ludicrous (several hundred dollars) but most companies got good discounts.
The thing that bothered me with the model was it disincentives modern microservice architectures. One big monolith cost less than lots of smaller components.
In both cases RFC1918 was used throughout their global network and while not fully used, had become highly fragmented over time.