Profile interface wise "definitly yes", GLSL wise "very likely yes" as GL profile version and GLSL version are not that hard interlinked as the spec states in most driver implementations.
I've tried to force a version with the directive #version 110/120 (wich is base 2.0/2.1 GL) in the shader and it still works here. So I guess FXAA should also work on older machines.