Yes, you are right. LO = longiflorum oriental...OT = oriental trumpet...OA = oriental asiatic.
You can easily spot the difference by looking at the format of the plant and its flowers. LO hybrids usually have long funnel shaped blooms and their leaves and stems resembles those of longiflorum. Prone to virus. OT hybrids are giants (thats why we call them tree lilies) to which oriental genes give a beautiful scent and flower size, and trumpet/aurelian genes give them a tall stem and a large number of buds. Aurelians means they have henryi
genes inside them and those flowers have recurved petals (usually). OA hybrids...don't know what specific to say about them. They have larger flowers then asiatics and some of them can have fragrance. Very hardy. I hope i explain it right.
The easiest way to recognize different hybrids is using photos. I won't link or copy/paste any photo here. Just go to database and find:
'Triumphator' - typical LO hybrid.
'High Tea' - OT hybrid with strong trumpet genes.
'Robina' - OT hybrid with strong oriental genes.
(you can see "genes" looking at stems and flower shape)
'Scheherazade' - OT hybrid with strong aurelian genes.
Can't remember any OA hybrid at the moment.