Issue was resolved - the reasons there were several:
- preferred image format: to get transparency outside image on the layer it required to specify TileImageFormat.Png explicitly (default is Jpg and layer is filled out by white color so base map layer become invisible)
- cql_filter parameter (it cannot be parsed correctly when it is specified in url template, most likely due to = symbol in value) passing it via custom parameters resolving this obstacle
- tiles for some zoom levels can be absent on the tile provider (as result layer becomes invisible)