Can you use wirsbo/uponor/expansion pex for underground sprinklers?
Yes to pex all types, some sources:

https://www.landscapemanagement.net/benefits-of-evolving-irrigation-pipe-products-2/
http://blog.supplyhouse.com/pex-crimp-vs-pex-clamp/
http://blog.supplyhouse.com/direct-burial-of-pex-tubing