The date the shares were purchased would be the date that would be used for the basis of the shares.
If the shares were later distributed to the beneficiaries, then the beneficiaries would take those shares with the trust's basis (i.e., a carryover basis).
The shares would not be considered as "acquired from a decedent" (subject to a stepped up (or down) basis) if they were acquired after the death of the decedent.
