You have a few options:

1. Ornatrix allows you to convert the hair to curves or mesh. Maybe you can convert the curves to C4D hairs.

2. Export the hair as alembic.

3. Export the hair as a proxy. Whatever type of proxy your renderer supports.

4. If your renderer supports rendering curves as hair then you can just convert the hairs to curves and render it this way.

Jeordanis Figuereo (Product Designer. EPHERE Inc.)

1. If you can export C4D hair to Alembic then you can import it back as Ornatrix alembic. That will convert it to Ornatrix hair.

2. If you can convert C4D hair to curves, then in Ornatrix you can use the Hair from Curves preset to convert it to Ornatrix hair.

3. If you can convert C4D hair to polygon strips, then in Ornatrix you can use Hair from Mesh Strips modifier to convert it to Ornatrix hair. 

Jeordanis Figuereo (Product Designer. EPHERE Inc.)