。
In that moment, the snowplow really was our hero.
Literal
This time, snow-plow [topic-は] certainly we [of-の] hero was.
除雪車 is a compound literally 'snow-remove-vehicle' for snowplow — one of many ~車 'vehicle' compounds for specialized trucks. このとき 'at this time' here points to a specific past moment, and the past copula でした makes the whole sentence retrospective. 確かに 'certainly, truly' emphasizes that the assessment is considered and unqualified. 私たちの英雄 uses the possessive の to frame 'hero' as belonging to the group — a common sentimental construction.