anycasting behind different ASNs?

[matthew zeier <mrz () velvet org>]

Are there any practical issues with announcing the same route behind 
different ASNs?

Shortly I'll have two seperate sites (EU, US) announcing their own space 
behind their own ASNs but have a desire to anycast a particular network 
out of both locations as well.

(This is just my attempted to now have to deal with GRE tunnels between 
sites that aren't logically connected anyways and using the same ASN).