as far as I know, they only blacklisted Geohot's psuedo-NPDRM keys but not the APP keys or every blu-ray games will not work. But yes, if the app is signed with proper 3.55 private keys either if its NPDRM or APP. Then it will work above 3.55, even the latest 4.31
I tried doing this by transferring games that I converted from BD to PSN, tested using E.X. Troopers, edited the eboot to redirect every dev_bdvd to dev_hdd0 and resigned the eboot using 3.55 private keys using scetool. Transferred the game via PS3 backup and whola. It just works!
And m sure that the appldr from 4.xx CFW is not patched on all CFW that is available today, that's why most of the homebrews doesnt work after it was upgraded to 4.xx CFW. appldr is doing its job to block any non-legit eboots. But yes, this method is easy to be patched by updating the appldr to scan the eboot if SCE header is still present, if not then they going to block it. As of now, scetool cant do sign eboots while preserving the sce header.