Oh yes, that would be a lovely repurpose for plastic, I'm not sure if we have bred bacteria for this purpose but I think they have already engineered worms to eat plastic, so the bottleneck so far is a issue of scale and cost it seems.

I'd love to see this for roads but I don't think it would stand for the stress involving vehicles, maybe something for more like electronics and maybe military stuff? Both industries love to shave weight off stuff, while still being able to do their jobs with reasonable durability..