They probably also cannot transit IMC while in a formation
While flying past RAF Scampton a couple of years ago I did watch with some amazement the Arrows practicing formation loops . . . with the bottom half of the manoeuvre completely immersed in cloud. We were on top at about 6000' with cloud tops around 5000' or so. They seemed completely relaxed diving in standard formation straight into the clag and then re-appearing with perfection some seconds later heading up-hill !
So I reckon they would have no problem transiting in IMC conditions if they chose to . . .. . . . it just wouldn't look quite so impressive to the tax payers !!