This...
X2 to more diggers in giggle hats ‘n’ greens.
Whilst there are photos of engineers kitted up in flak jackets and even a combo of flak jacket and steel helmet (see attached images, one of 1 Field Sqdn RAE, one of 17 Construction Sqdn). The most common sight and most useable in a game would be the two man engineer splinter or mini teams attached to infantry companies and for the most part they would be dressed and equipped just like the infantry they were attached to. Third image shows a member of a splinter team.
That said, I have seen a photo of a mixed patrol of infantry and engineers patrolling by boat wearing the interesting combination of tin hats and life jackets.