What are these "X"s / crosses on this schematic's wiring? Traces attached to the metal housing (ground)?
Based on the more complete schematic it seems fairly obvious that the continuous line around the outside represents the metal shielding can. 

The X's seem to be where circuit traces or connectors escape the can, such as the connections to the regulator. The actual connections (other than the user connectors) seem to be a long header that pokes through a hole in the can. Video showing modulator