first, it would depend on what prison and what area of the country we are talking about. with all of these mobsters locked up it would make sense that in some facilities they have high enough numbers to be left alone. like was mentioned earlier, mobsters have some limited alliances with street gangs, in that case the bloods not the crips.
these alliances benefit both parties as the mobsters are sure to have connections that the gangbangers would find useful on the streets and the same goes for the mob guys in prison. if i remember correctly the deal between the bloods and members of the lucchese family had to do with moving cellphones, drugs and other contraband into a state prison in new jersey through a crooked guard. another agreement in the deal was that apparantly a blood member was hassling an associate of the family and that needed to stop as well.
another point i should include is that there always seems to be alot of talk about how the gangbangers would be fascinated by the mobsters, the same as alot of us here. makes sense as you constantly here about all of this OG(original gangster) crap that these hoodlums preach. who is more OG than a mobster?
long story short, while mobsters more than likely have some problems in prison, i doubt they are being taken advantage of the same as some white kid fresh off the bus from the suburbs.