What a great scheme.

Crows are susceptible to chronic liver disease if they live in urban areas (particularly near restaurants or markets). I looked it up because it's happened to a few crows in my urban area who have grown long, thin deformed beaks, and I was curious what was causing it - apparently a fat-heavy diet which leads to chronic disease is the most common cause. They can also get sick or diseased from scavenging tainted or toxic food.

I can't find any info for crows being able to contract diseases from humans, so it's low risk for them collecting cigarette waste.

So this scheme is win-win - crows adapted to urban areas pick up litter with no (or very low) risk to themselves, get safe and nutritious food.