This is how to read evaluated setup channels using MODO python SDK. The crucial bit is using scene.SetupChannels() in line 11. Stolen from Foundry's coding slack channel.

setupChannels.py

scene_svc = lx.service.Scene()
sel_svc = lx.service.Selection()
pkt_trans = lx.object.ItemPacketTranslation(sel_svc.Allocate(lx.symbol.sSELTYP_ITEM))
sel_type = sel_svc.LookupType(lx.symbol.sSELTYP_ITEM)

for i in xrange(sel_svc.Count(sel_type)):
    pkt = sel_svc.ByIndex(sel_type, i)
    item = pkt_trans.Item(pkt)

    scene = item.Context()
    chanRead = lx.object.ChannelRead(scene.SetupChannels())
    index = item.ChannelLookup(lx.symbol.sICHAN_XFRMCORE_WPOSMATRIX)
    if index > -1:
        matrix_val = chanRead.ValueObj(item, index)
        matrix = lx.object.Matrix(matrix_val)
        print matrix.Get4()