Can we use pre-filtration in combination with filters that are less than MERV 13 in order to earn the credit? For example if we use carbon pre-filters combined with MERV 11 would that work?

This could work but the burden will be on your team to demonstrate that the filter combination is as good or better than MERV 13. Try focusing on the percent efficiency that the filter combination has for removing varying sizes of particles and compare that to the corresponding efficiency of MERV 13 filters.