I think when they say 300 micrograms = 10 mg morphine they mean in opiate naive individuals. Someone who has no real tolerance to opioids would probably actually get higher off of the buprenorphine initially than the morphine, or at least, as high, but for a longer period of time. It's hard to equivilate buprenorphine to other opioids because of buprenorphine's cieling effect which seems to be different for everyone, but probably somewhere around the 6-8 mg mark (and when i talk in large doses like this I'm refering to the SL roa, the I.V cieling would be around 2 mg probably.) I have read though that at the point where buprenorphine levels off, it's equivalent to approx. 30 mg of methadone. So if your cieling effect is at 8 mg, that would be similar to 30 mg of methadone.
The reason most people that have an opioid tolerance don't get high off of buprenorphine like they would off a full agonist is because of this ceiling effect. It's probably safe to argue that they also wouldn't get "high" off of 30 mg of methadone either.
What I find annoying about suboxone is that it has such a long half life. Someone on some forum here (i think) did some algarithym that showed how buprenorphine builds up in your body. Basically if you take 16 mg a day, according to this graph, once you stabalize on this dosage after 11 days, you have about 40 mg of buprenorphine built up in your system from all the long half life. So according to that math, even a moderate dose of 4 mg/day, would still build up to an overall 10 mg in your system, basically meaning that the ammount of buprenorphine in your system is still at the cieling level. I don't know if all that is bullshit, please correct me if the information I posted was wrong, I'm just reporting something I read.
It would be awesome if bupe had a short half life, but somehow still a long duration, that way the dosages wouldn't build up, and if you stayed under the cieling limit, you could just pop another two mg and get a bit more buzzed off of it, but that's all just a dream anyway.