How is BGP potentially injecting information into the IGP? The only way that should be happening is if you are doing BGP -> IGP redistribution, in which case I'd surely hope you aren't doing IGP -> BGP as well.
you are an isp in a small country with half a dozen other isps. the biggest isp in the country has half a dozed prefixes. you all meet at an exchange point and each has an external international exit through an upstream. you want to redistribute the bgp routes learned at the exchange point into your dynamic igp so, when the ix is working, local traffic goes directly there as opposed to tromboning through your default exit. one then also wants to receive from one's upstream transit (or inject) a bgp default route into one's igp, and then one wants to inject one's internal routes into the bgp exports to both the exchange and the upstream. if one's network is at all likely to partition, that means one wants to redistribute one's igp into those two bgp sessions, heavily acled of course. randy