Veloo
As Scott rightly points out this sort of occurence happens all the time. When first introduced these were called "nuisance" events - however, you never know when TCAS may save your bacon!
An interesting fact about your incident is that it appears an RA was issued prior to a loss of standard vertical separation. There is a lot of literature out there on what actually happens during a TCAS incident and it requires an amazing amount knowledge amongst all parties to be truly effective.
Suffice it to say that your MAS aircraft was probably descending at a fairly high rate - this led to the on board system on the SIA aircraft getting "nervous" and an RA being issued.
If TCAS was operating exactly as we would like then the following would have happened;
*As the MAS was approaching its cleared level the aircraft's descent rate was reduced.
*The TCAS system on the SIA would "spot" the approaching confliction and a TA would be provided to both crews.
*As vertical separation was still reducing, but at a shallow rate, (even still in excess of 1,000ft) the MAS would be given a "Monitor vertical speed" Resolution.
*This would require the crew to follow a vertical profile that the systems had decided upon to maintain separation.
*As the approaching angles were, in effect, shallowed out no drastic RA action would be needed.
It's not an ideal world though is it guys!
One thing you can do to possibly help in a situation like this in the future though would be to provide Traffic Information to both aircraft (time permitting) to help begin the above.
I've used things like;
"ABC123 maintain FLxxx on reaching there is traffic crossing left to right 1,000ft below in 90 seconds 10 o'clock range x miles, caution possible TCAS alert"
a pre-emptive strike (in this situation) never hurt anyone!