Disks can be encrypted to either just a passphrase, or a public key. If just the passphrase, you need it for access or decryption. If to a public key, you must have both the the paired private key, and the private key's passphrase. The other possible option is that if the laptops had PGP installed in a PGP Universal managed setting, that setting might have also created Whole Disk Recovery Tokens, that could be used to access and decrypt the disk. You would have to receive this WDRT from the PGP Universal admin.