Beware that toll free numbers outside ths US are charged per minute and at generally high rates. It might be better/cheaper to dial the us toll free number from abroad and connect to the Um number

Its mainly for using on public phones or hotels and stuff i'd say.
From your homephone its mostly cheaper to use local providers anyway, istnt it?

Chris

Can you use cbw trigger a callback to phone A by calling the callback number on phone B?

Thinking of using UM and a uk roaming mobile to trigger the callback to UM

Yes. The relationship 1. CALLBACK TRIGGER # to 2. # TO BE CALLED BACK is the key. When any phone dials 1, 2 will be called. My understanding and experience.

Also, if your roaming mobile has GPRS you can trigger a callback by just "touching" a URL. I previously posted instructions on how to do this. This avoids the possibility of being charged for an unanswered callback trigger, which sometimes happens although it shouldn't. The byte count on the GRPS trigger is so small I've never been billed for it.

Some of the CBw toll free numbers do not work on payphone in Europe (e.g Netherlands). This is the first. It is generally cheaper to call us toll free numbers from european carriers rather than use the toll free number for this country. So the answer to your question is: Yes

Basically you're right but the toll-free (or, as in case of Poland, almost free ;)) access number is also a backup in case when callback doesn't work for any reason....
At least it turned out to be a backup for me once or twice....