The Olive Tree is not Israel anymore than the Commonwealth of Israel is Israel.
Both symbolize Israel's access to blessing and its conditions.
Just as the Wild Olive Tree symbolizes Gentiles being far off from said access and in a wild state spiritually.
Read Charles Welch (who infected E.W.Bullinger with the Acts 28 Position) - read any of their works - and you find the same basic flaw throughout all their conclusions.
Their consistent failure to note that often, when Paul quotes the OT, he is doing so, not as a means of pointing out that what he is preaching was prophesied, rather; he is noting within their writings a same principle that applies during this Mystery age in a different way.
"But as it is written" as applied by Paul, for example, is not always a reference to what was prophesied, rather to a principle it shares in common with what was not prophesied.
The principle is the same in both.
At the same time, its application differs in each.
Case in point - failing to see this; most conclude that MAD asserts Israel was under a salvation by works. Even some MADS conclude this.
In fact, it is the application of the same principle in both in a different way, that such fail to see.
The principle in both Prophecy and Mystery in this case, is faith.
Its application, however, differs in each.
In the one, it is - if you believe God through Moses, you will walk in "the Law for righteousness."
There, the real issue is faith.
In the other, it is - if you believe God through Paul, you will walk in "But now the righteousness of God without the Law."
There also, the real issue is faith.
This is a basic principle in both. Its application, however, differs, in each.
It is a principle so basic that many forget to consider it whenever Paul quotes the Law and the Prophets.
Applying it, I find that Galatians 3, for example, is just like Romans 4 - Abraham BEFORE he was "in circumcision."
But Paul is dealing with those influenced to put themselves under the Law. As a result, he brings up those issues that he brings up there.
Just as he aniticipates these same issues in Romans 4.
In both, Paul once more applies this practice unique only to him and the Lord (in Matt.-John).
In Gal. 3., he extracts out of "seed" the one seed "which is Christ" (clearly a reference to a multiplied seed everywhere outside of Paul).
There "seed" is different in Paul's
application of it.
He can do that because the principle - Christ - is found in both the multiplied aspect and the singular aspect of...seed.
He has applied this "same, but different" principle unique to him and the Lord.
The 28er does not apply this principle anywhere. Let alone, to Gal. 3.
As a result, he sees Gal. 3 as talking about the Abrahamic Covenant the Galatians are supposedly under.
Likewise as to Romans 11's grafting in...and Acts 15, and so on...
I've been dealing with one of them off and on. I invited him to post on here but he said this forum does not come off as one actually into exploring differences in understanding.
I'll have to agree with Mid-Acts' C.R.Jordan as to that kind of thing "Opposition is good for ya; it gets ya tuh thinkin some things through a bit more than ya might..."