Ther are thre things that argue against such as supposition.
1. the low numbers of runaways enumerated in the 1860 census no matter what the reason for those low numbers of runaways.
2. the lack of wide spread use of the underground railroad prior to 1860.
3. the lack of a revolt on the plantations during the war especially after the Emancipation Proclaimation when all the "white folks" were gone off to war.