The short answer to this question is 'yes'; however, machine settings and inspection standards may need to be modified to ensure effective use.
All the lead-free solders of current interest (tin/silver; tin/copper; tin/silver/copper; tin/silver/bismuth; tin/zinc, etc) can be examined using x-ray methods, but because of the absence of lead, the image density is likely to be different to that when conventional solders are analysed. Machine settings (voltage, current, aperture, and image enhancement/analysis software) can be optimised to increase image contrast, but in cases where the image background affects observation of the joint, then either an alternative viewing angle or changes to the inspection pass/fail standard may need to be employed.