I'm deferring my comments on media history in order to address an issue that has come up in the blogosphere, namely whether Paul quoted from the Gospel of Luke. The passage in question is 1 Timothy 5:18, which reads: "18 for the scripture says, 'You shall not muzzle an ox while it is treading out the grain,' and, 'The laborer deserves to be paid.'" The former of these quotations comes from Deuteronomy; the latter is found within our extant literature only in Luke 10:7.
Now, before I started my current book on Lonergan, Meyer, and historical Jesus, I was indulging my obsession with the dating of the New Testament texts with a now-half-completed manuscript that might or might not ever see the light of day. The truth is that I've increasingly come to recognize that on most issues of interest to the historical development of Christianity the precise dating of the NT texts is actually not that important, except as an end on to itself. That said, I did come to the conclusion that the relationship between 1 Tim. 5:18 and Luke 10:7 has an import under-appreciated in the study of NT origins.
Let us deal with the most basic issue first. It is often objected that 1 Timothy could be quoting something other than Luke. This is possible, but is it probable? Perhaps it is quoting oral tradition or one of Luke's sources, or even an other, otherwise unknown, text. The former seems unlikely: the quotations are introduced as coming from the "writing[s]" (probably a a better translation than "scripture"); given this language it seems most probable that what is being quoted comes from a written text. The other possibilities would seem to run afoul of the principle of parsimony. We have this quotation in an extant text; it is quite conceivable that whomever wrote 1 Timothy knew that text; so why multiple entities on this matter? The strongest (albeit not only possible) hypothesis is that 1 Timothy here cites Luke.
Another possibility has been floated by James McGrath: that Luke was influenced by 1 Timothy. Whilst possible, again it seems unlikely. First, Luke 10:7 parallels Matt. 10:10, with one change (Matthew's τροφης is Luke's μισθου). If Luke got his usage from 1 Timothy then where did Matthew get his usage? From Luke, perhaps? Moreover, 1 Timothy explicitly presents the passage as a quote. If Luke copied from 1 Timothy then we would still have to explain the origin of that quotation. The alternative, quite possible, view, that 1 Timothy cites Luke thus has both greater explanatory power and greater parsimony, and as such is to be preferred.
Now we reach the date of the texts in question. If indeed Luke is post-70 and if 1 Timothy cites Luke then 1 Timothy must post-date 70. This however is only possible if Paul did not write 1 Timothy, or if somehow Paul lived into the post-70 era. The latter can reasonably be ruled out: all the best data should lead us to infer that he died sometime in the mid- to late- 60s. The former stands as a broad consensus in the discipline. Indeed, I would argue that given the consensus views on the matter of NT chronology the most probable hypothesis is that 1 Timothy is a pseudo-Pauline text written subsequent to and quoting Luke's Gospel.
This could well stand despite my own thinking on the dates of the gospels. I have come to the conclusion that Luke's Gospel was probably written by c. 60. That is because I think (negatively) that the references to the destruction of the temple do not necessitate a post-70 origin, and (positively) that the ending of Acts is most explicable if written whilst Paul was still alive. The interesting thing is that even if Luke was written in, let's say, 60, it would not necessarily follow that Paul wrote 1 Timothy. There would still be the possibility that 1 Timothy is a pseudo-Pauline text that knows a text that happened to have been written during Paul's life. Thus although I don't think it impossible that the historical Paul could have referred to Luke's Gospel neither do I think it as certain as Glenn Peoples.
In truth, New Testament chronology and inter-textuality are difficult, dodgy, matters. There are always a lot of balls in the air at any given time. The only tools that I have found particularly useful in adjudicating between hypotheses are those of explanatory scope and parsimony: what explains the most data with the fewest entities. The above, with 1 Timothy quoting either a pre-70 Luke or a post-70 Luke, seems the best here.