Regarding using RFC 1918 blocks - some of the mid-to-large size carriers have, either due to their size or due to wasteful subnetting, fully used the available

Regarding using RFC 1918 blocks - some of the mid-to-large size carriers have, either due to their size or due to wasteful subnetting, fully used the available RFC1918 blocks and have begun using otherwise unrouted spaces such as the DoD subnets to continue addressing devices on their network. For example, in Canada, Rogers has begun to use the 7/8 subnet for CMTS addressing because the RFC1918 address space isn't large enough. I believe some carriers solve this by having topographically independent networks that re-use the RFC1918 space in different sections of the country, however not all carriers have done this.