Thanks for the prompt reply Steve!
So the hwy bus lanes increase bus speed on hwys. I don't think I'll be using this, first of this requires a big busstop network, and a lot of highways, along with a relative lack of other MT types. eg subways or GLR, to be attractive. Quite unlikely for a large city (to have a need for hwys). And I'm afraid you will see lots of buses on the hwys (uhhh). And the park & ride feature would require a totally different city building strategy (lots of parking and MT everywhere). ie it wouldn't be attractive to most players.
Of course my most important question in ths post was about the commute/cross-city-borders thing, but indeed this is broken in SC4, as you said. Connections are needed, to raise demand caps and export industrial freight, but sims too seem to prefer them. I think the best one can do is a different city layout: build industry at the city edge; I usually zone I at the corners, to minimize the pollution effect but often sims are reluctant to work there because... they're far away (they prefer the neighbour city although commuting there is finally longer); but you can expect that they will finally work in their home city too, esp if you zpne more R zones closer. Also some C along their route to the neighbour city can be a good solution: not only it can act as a "trap" for the outgoing sims (it's closer than crossing the city border) - although it is often occupied by sims from... the other city - it will also prosper due to the high traffic (I often get more development there, than in the CBD!). However all these just ease the problem a little, don't solve it. I have even considered extreme measures, like using traffic blockers (so that you have the benefits of connections, but not the traffic), but these look just funny (havng a connection AND a blocker). Careful city planning is rather the best workaround (not a "solution" unfortunately)...