Some good points above.
Personally I would try to pre-empt the RA and turn an a/c that was maybe a level or two above..Obviously this would require some very quick thinking which,lets face it,is easier said than done.If you have cleared 2 to the same level you will not necessarily believe what you are hearing/seeing.
Also,what will a pilot be hearing from his TCAS with traffic below and above? Would he be in a position to also listen to ATC instruction on turns and listen to traffic information.I doubt it.
The reference in MATS 1 is there for a reason based on past lessons.It would be very hard to argue against it.