Greg,
What you typically see are viscosities of these various oils @ 100C, expressed in terms of "centistokes". This is the low shear rate, or "kinematic" viscosity and is used to classify the oil by SAE grade ie 20wt/30wt/40wt/, etc.
HT/HS viscosity is measured in "centipoise", with the oil @ 302F/150C and being sheared @ 100,000 cycles/second. The HT/HS viscosity is an better analog to how the oil will perform in terms of bearing viscosity and also up in the valvetrain - say between the cam lobes and valve lifters. That's why I consider it to be more relevant than the kinematic viscosity ....
The ACEA "A5/B5" specification calls for a HT/HS of from 2.9-3.4 Cp @ 150C, so there is quite a bit of variation in the specification. This is the new class of low viscosity, long drain oils being sold in Europe for most newer engine designs. You really have to look at each individual oil to see where they fall within this range. For example, I think that Mobil 1, 10w-30 comes in @ 3.2 Cp, which is outstanding for an oil with a kinematic viscosity of only 9.7 Cst @ 100C. What this tells me is that this is a very shear stable formulation.
The ACEA, "A3/B4" spec is somewhat simpler than A5/B5, since you know the HT/HS is at least 3.5 Cp and you are going to get the high load/high temp protection. The new ACEA, A5/B5 test matrix is basically the same as the older A3/B4 test series, so it is much more stringent than the SL/CF specs used in the US. Of course all you know is that the oil has passed the test - but you don't know if it barely passed or passed with a comfortable margin to spare ....
I hope this answers your question ....
Ted