Some people were talking about shooting the Cowtown in January well the Dallas White Rock Marathon is next Sunday.
http://www.runtherock.com/index.html
Course Map
http://www.runtherock.com/race_info/map.html
Now the prime spots would be of Course Start/Finish Line but then you have several spots on the west side of the lake, east side on the north end is possible to get in and out of but anything back behind the Arboretum between Winfrey Point and the entrance to the park will be pretty much foot traffic entry only so that would be not the best spot to set up (plus if the wind is from the North west across the lake it can get chilly over there). Some of the aid stations along the lake are pretty elaborate, for years there has been one that dispenses beer to the runners!
Now the area along Lakeshore between miles 20 and 21 brings up "THE HILL" that baby takes a lot out of the runners coming in up off of the lake. Also nice large homes along the street, hey may still have some color! Then along Swiss Ave is always a great area to shoot, you can park over at the Wells Fargo Bank or in the Lakewood Shopping center and walk a couple blocks to Swiss.
Noticed that they have the Half Marathon running across town and down Swiss which will put even more people on the street to shoot.
I don't know if anyone would be interested in shooting the event but they should have a lot of runners.