The wording of the section on Mana Barriers is talking about magical force to break through the barrier, not physical force. The comparison it makes to any other physical barrier is to inform you to use the same system for tracking damage to the barrier.
On page 315 in the entry you mention there is a chart which describes the caster's options for where the barrier will be present, and lists the specific page governing the spell or effect which causes the barrier. Mana Barrier itself can be found on page 294 of the 5th Edition core rules, and describes a barrier which does not prevent the passage of non-living (physical objects) or living things unless they are 'magically active.' For comparison, the next listed spell is Physical Barrier.
Unbound/uncontrolled spirits active in the area are affected by the barrier and have to contend with it like anyone else. Whether or not a summoning could take place on the other side of the barrier would very much depend on the situation and the barrier.
If a mage (or other affected being) desires to pass or have an item which is affected pass through the mana barrier they have three choices:
The subtle way is trying to magically bypass it as described on page
316, where every additional hit allows them to slip other affected
items or beings through with them. This is described as pressing
through the barrier, much like Dune's 'the slow knife will penetrate
the shield.' This approach does not automatically notify the creator of the barrier
The forceful way is to target the barrier with damage-causing
magics. This is handled 'just as you would with any other barrier,'
by dealing with its Armor and Structure ratings. These ratings are
equal to the Force of the mana barrier. The barrier must be overcome
in one Combat Turn or else its Structure refreshes. This approach
automatically notifies the creator of the barrier.
The third option (page 317, sidebar) is to attack the source or
basis of the barrier. In other words you can deal with the anchor,
destroy the lodge, or geek the mage responsible for sustaining the
barrier. With the source out of the way, the barrier is no longer a
problem. This approach, if it brings down the barrier, will notify
the creator automatically.
These choices are the same regardless of where the barrier is on the Astral Plane, on the Physical Plane, or on both.
Mundane gear and allies are unaffected by Mana Barriers.
Affected beings or items cannot normally pass through the barrier, unless they Press past it or bring it down. In some cases a mundane object may force them through the barrier (page 316) in which case they must pass an Opposed Test or be disrupted.
The effects of disruption are listed in the Astral Intersections passage on page 316. Foci are deactivated, spells end, spirits are dispelled, and living beings are Stunned. Afterward, foci can be reactivated, spells can be cast again, spirits can be summoned again, and living beings will recover from Stun... providing the owner of the mana barrier gives them the time to do all of this.
No amount of time is listed as a penalty for passing through a mana barrier, just the condition resulting from that intersection. Using the details of that imposed condition indicates a deactivated focus can be reactivated by the person it is bonded to as a Simple Action - if they are conscious. Likewise, spells and spirits can become available again in the time it takes to call them forth. Living Beings will recover from Stun normally.
Because you might not always have the money built in to your character at char gen to put into buying an RCC. It is not a REQUIRED piece of hardware for a rigger. In fact, riggers can rig just fine with only a commlink. It's just that it becomes a lot harder to control an entire group of drones, or multiple drones, or give them extra abilities. It's not unheard of, it's just rare.
My suggestion to you is to always have an RCC for your rigger. Characters generated in the example section is supposed to be more of an inspiration then a full-out, well made character. If you are going to be a rigger, you should be putting high priority into money anyways, so this should never be much of an issue. But, I have seen adept riggers too, and they'll only have the data port to jack into a vehicle (usually a car or plane or something) and rely on adept powers and bonuses to do better driving or flying.
Yes, a datajack is cyberware that only provides a DNI (direct neural interface).
The Rigger Control Rig (as well as the implanted commlink or implanted cyberdeck) also provides a DNI, so it provides all the features of a datajack.
The sentence immediately before the one you quoted is this:
Which is pretty much exactly what a datajack is (plus it mentions storage, but raw storage has been abstracted away in SR5).