It varies. The narcotics business is too large for any one group to control. By the sixties and seventies there were changes in the criminal world-a sort of perverted echo of Black power. Many Black criminals no longer saw a reason why they should constantly be in a subordinate relation to the Mafia.
Still business is business. Despite his protestations of independence, Nicky Barnes relied almost exclusively on the Mafia for supply, particularly Lucchese member (associate) Matthew Madonna. Barnes tried to become completely independent but could not get enough support from his compatriots. He had to settle for cutting slightly better deals.
On the other hand both Frank Lucas (Golden Triangle) and Frank Matthews (Cubans, Turks and Colombians) had their own suppliers and were known to not be overly fond of Italians. Matthews in particular had a dislike for the Italians. Matthews still did business with them but on terms he found better for him. When threatened with violence he responded in kind and based on his rep the Mob backed off.
Matthews became a national narcotics wholesaler and went so far as to chair a 1971 Black criminal meeting in Atlanta devoted to teaching other would-be crimelords how to get independent sources of narcotics.
The drug business is too large for one group to control now. It was a different story when the Mafia had a virtual monopoly on the heroin business for a half century, from the 1930's to the 1980's. And I'm talking about control of the supply of upper wholesale level. Similar to what Mexican drug trafficking groups have now throughout the country except in the Northeast and South Florida.
As I said before, black groups have been primarily involved in mid-to-lower level drug trafficking. Whether it was Barnes getting his supply from the Italians or Matthews getting his from other groups, they were at the mid-level. They didn't control importation. As for Frank Lucas, there has been a lot of debate about how factual his connections were to Southeast Asia, as well as how significant they were if they did in fact exist.