Generally you will find that CDN's will give you a dedicated IP address for each container you setup, however they will share the same C Class IP address depending on where the content has been downloaded from as CDN's work by closest region so you generally get more than 1 IP address per a region.
So with this said you will get a dedicated IP address but will share the same C class, now the other thing is you will get the same TLD i.e
your-container-id.cf3.rackcdn.com So the foot prints here are the C class IP and the TLD domain. If you are daisy chaining the sites with one another and you have gone to the extent to have different C Class IP addresses and you believe that Google uses this in their algorithm then yes, it leaves a footprint.
It should be possible to speed up your site(s) without CDN with decent hosting if you are concerned about Google.