Traffic data comes from a completely different source (or sources) than map data. Some traffic data comes from sensors along freeways and from state police/highway patrol reports, and (at least in the cases of Apple, Google, and Waze), some of it comes from anonymized data from the people actually using the maps app and are actually driving the roads. One of the reason Google's traffic data and arrival estimates are so good is because everyone using Google Maps is sending back their data so that Google knows the current average speed and problem areas of millions of roads that lack their own sensors (which are usually only installed on major freeways), so virtually any road with enough traffic can report current traffic information for the use of other users. Waze of course crowd-sources other information, such as speed traps, construction, and other issues.
None of that has to do with the drawing/redrawing of roads on the maps and other associated data - that's done by different people, whether in-house or outsourced.