Hackers - sitting or running? Options

[Tseims]

Do hackers need to be with other runners or can they just stay home and hack the doors open for the other runners?

My group's hacker has been hacking quite cozily from a van that has an antenna that has Signal rating 5. We thought that the van only needs to be within 4km of the hacking target, but then I read this in SR4A p.222:
Signal represents the broadcasting power of the device’s hardware. The
higher the Signal, the farther the device can transmit. Signal ranges
and examples are listed on the Signal Rating Table. When two devices
are within the range of the lowest Signal rating of the two, they are
said to be in mutual Signal range; this is required for direct device-to-device
communication and for other applications.

So, imagine we had a run in a corporate headquarters. Would the hacker have to come with us to hack all the cameras, doors and such with Signal rating 2 OR would it be sufficient to park the van within 4km if the HQ had an antenna on top with Signal rating 5? How are buildings networked?

Also, is "bridging" (using different nodes to connect yourself to a node far away) connections allowed?