Interesting situation you have. I have never heard of anybody logging route changes but you can start with a simple bgp -adj change
config router bgp
set log-neighbour-changes enable
Then can look at a nagios check_bgp sheck and poll each bgp neighbor and if the total count doesnt match X , than take action/alert. I use something like that for BGP checks on Juniper MX and cisco ASRs, but you will have to play around with it and perform some trial and errors.