in both vendors, i would suggest to make use of layers rather than trying to tune PBGT HO.
LAYER in ericsson (HCS)
HO cause 14 (umbrella to micro) or cause 21 (900 to 1800) in ALU
both are rather complex, so i can’t explain them on a forum. But if you read the docs, then that ought to point you in the right directions.
Moreover, I would say that what you want to do is not possible. In one case you want to go to the outdoor, and in second case, you want to stay in indoor. But both scenarios present identical radio conditions. It is not possible to distinguish them. The best idea IMO is to tune a very short window time in the Indoor, whatever the HO thresholds you use. The idea is to keep the call “alive”. You’d rather go to the outdoor by mistake than force the MS to stay too long in indoor. Minimize the risk of drops.