Typically they tell you to connect the IG to the same spot in the service disconnect enclosure where the MBJ lands.
For the NEC purposes a Ufer is a pretty good electrode but I would not count on 30' of that rusty rebar to give you a single point ground. There are at least 2 snap tied joints in there.
Do you think a simple resistance test between the two electrodes would be sufficient to verify their quality of being a common point?
