Moved from Pērnavas iela to Sapieru iela through the area in question. 
1st photo taken from between Pēranvas 15a and Čaka 156, view towards the Sapieru.
2nd from gates.
3rd in the middle of the yard.
4th is view of passageway from yard towards Sapieru iela.
5th is gates/passageway view from Sapieru iela towards the yard/Pērnavas iela. Note the plate indicating that it's Sapieru iela 1 building. Passageway has gates but they are open.
No plates saying that it's a private property from any side.

Attached photo(s):
https://westnordost.de/p/231350.jpg
https://westnordost.de/p/231351.jpg
https://westnordost.de/p/231352.jpg
https://westnordost.de/p/231353.jpg
https://westnordost.de/p/231354.jpg