Simplicity of the approach  ` tau /. list` and `b /. list` makes it quite natural to exploit. Nevertheless one can take into account another approach which can appear to be more efficient for long lists:

    listtau = Last @@@ First @ Transpose @ list
    listb = Last @@@ Last @ Transpose @ list
>     {32.8775, 24.4891, 12.6688, 4.84722, 0.134423, 0.103983, 0.0610192}
>     {0.299216, 0.277134, 0.356032, 0.30632, 0.965791, 0.587649, 0.999985}

It might be reasonable to consider also:

    list[[All, 1, 2]]
    list[[All, 2, 2]]