Re: Shi'ahs
Im not aware of any hostilities between the two groups, if there was any. Ismailies are not really that large a group to cause such a rift i dont think, beside all shias at the time of Imam Kazim were a minority and persecuted and hence im guessing they had bigger things to worry about.
There are hadith on the black flags of khorasaan is a sign of the time, but not sure if the Imam accompanying them is mentioned.