EDITED: per Wikipedia it's more complicated (see ADDED below), assuming as speculated elsewhere in this thread that they used visual means for air search, or I would note another albeit unlinked radar system:

"The Buk missile system was designed to surpass the 2K12 Kub in all parameters and its designers including its chief designer Ardalion Rastov visited Egypt in 1971 to see Kub [SA-6, very effective in the Kom Kippur War 2 years later] in operation. Both the Kub and Buk used self-propelled launchers developed by Ardalion Rastov. As a result of this visit the developers came to the conclusion that each Buk transporter erector launcher (TEL) should have its own fire control radar rather than being reliant on one central radar for the whole system as in Kub. The result of this move from TEL to transporter erector launcher and radar (TELAR) was a system able to engage multiple targets from multiple directions at the same time."

If they have a vector to feed the fire control radar, and it then succeeds in acquiring the target, I would expect it to work. Our anti-radiation missiles, plus the system's missiles until the most recent one having semi-active homing (fire control radar must paint the target), put a premium on this sort of arrangement.

ADDED: I too am just learning these fine details; further down, as quoted by powertower in reply to this posting, the above ideal wasn't implemented in full, there's a normal 2-1 ratio of TELARs to TELs. And think about the implications of the TELARs being obviously more expensive: the normal ratio is unlikely to be always observed, the maintenance demands of TELARs and a high TELAR to TEL ratio is going to be higher, etc. etc.