I have a similar shot (below) which I kept in colour but shot from a different position so that the sun was away from the cross. Also taken with the G1X.
The first b&w image was taken at f/11 and the maximum focal length of 60.4mm. A small aperture generally increases the starburst effect. The image below at f/6.3 and 30mm focal length but the starburst effect is still present at the larger aperture.