There is a big difference between 'caches in ISP networks' and 'caches in public datacenters adjacent to local exchange points'. The first implies preferential

There is a big difference between 'caches in ISP networks' and 'caches in public datacenters adjacent to local exchange points'. The first implies preferential treatment from ISPs, the second is commodity available to everybody. Your link implies these local PoPs are more likely the second case.