We now have the "Handover Decision 2" in osmo-bsc, using many more indicators than one BTS' RXLEV and RXQUAL
So far osmo-bsc only looked at a single BTS's RX level and quality to invoke handover; but handover is much more complex than that: even if all subscribers have nice rx levels and qual, it makes sense to spread load, and to keep a number of lchans open on each cell. It can also make sense to simply re-assign within the same cell, just changing between TCH/H and TCH/F. Here is an overview of the current state of load-based handover in osmo-bsc.
slides: http://people.osmocom.org/neels/2018