If there are any master tapes. Some reissues are from master tapes, others are from different source files including old tapes and records. Digital mastering can still clean up those things, but the original is best. Of course, depending on the age, some master tapes might be worthless. The old way of recording was on tape, before all the digital recording. Tapes wear out with age, even if they are not used. The media basically turns to goo and becomes unusable.
However, to answer your question, yes, the reissuer would get the master tapes or whatever is available to transfer digitally to CD.
ult
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