In theory, the 4x4 kicks in whenever one of the front wheels spins (I note yours is 2010 model, so uses electronic engagement of 4x4), so yes, it shoudl work in reverse too.
However, if one of the rear wheels is not able to grip (likely on snow/ice), then all the 4x4 system will do is spin the slipping rear wheel. The Cross lets you 'lock' the spinning wheel by pressing the ELD button -- and on other models , inc those with viscous coupling like my 2005 model -- you can simulate this effect by lightly applying the handbrake!