The Christmas formats I hear on secular stations fall completely flat - all secular generic holiday stuff. I have a Christmas oldies format that I can run, and a traditional Christmas carol format that I can run. I doubt there is much audience for either.
As far as Christian artists doing Christmas songs, there are a bunch of remakes of things like sleigh ride. Personally, I feel more Christmasy with the Ronettes version, or Boston pops (1959) versions. Maybe Amy Grant's from her first Christmas CD. It is pretty much the same with just about every other song - Christian artists making White Christmas, Christian artists doing the Christmas song, etc. Give me the originals from the 40's and 50's every time. And I am not the only Christian saying it!
One thing is for sure, you won't get anywhere close to a Christmas Carol on a secular station that goes Christmas in December. The name of Jesus Christ is not to be heard in anything they play. A lot of them won't even play Silent Night. They would melt at the prospect of Hark The Herald Angels Sing. Have yourself a secular little Christmas should be the name of the format in December. It is depressing when I listen, because Christmas is about CHRIST. At least Christian stations going Christmas don't censor out the true meaning of Christmas. If it takes secular songs associated with Christmas to draw in the listeners, I say go for it.