Yes, they can interbreed.
No, you don't get "mixed breeds"
Contrary to ethnic races, metagenes seem immune to recombination, miscegenation, and dilution. Although members of different metatypes are able breed with one another, the child always expresses only one of the parent’s metatypes—or is born human (as a result of conflicting metagenes suppressing expression).
(SR4 Runners Companion, 46)
So, a child born to parents of different Metatypes will either come out as Mom's Metatype, Dad's Metatype, or as an ordinary Human.
Perhaps also of note, is that this applies to Metavariants* as well:
Medical studies on the procreation of metavariants have also indicated that children of different metavariants of the same metatype either express the paternal or the maternal metavariant-type. Crossbreeds between different metavariants or baseline metatypes and metavariants appear to be impossible, though the reason for this exclusivity is currently unknown.
(SR4 Runners Companion, 48-49)
* Metavariants are sub-types within a Metatype, generally a lot rarer than the base Metatype and focused around a geographic location. For example, under "Dwarf" you can find: Gnome (Europe), Harumen (India), Koborokuru (Japan), Menehune (Hawai'i), and Querx (Germany). They are considered derived from their parent Metatype, but are different enough to count as 'unique.' In 5E, you can find details on them in Run Faster, starting at page 88.