First of all, Schabowski's mistake wasn't saying, that people from East Berlin were allowed to go to West Berlin, but reading the following:
[...]
2. Ab sofort treten folgende zeitweilige Übergangsregelungen für Reisen und ständige Ausreisen aus der DDR in das Ausland in Kraft:
a) Privatreisen nach dem Ausland können ohne Vorliegen von Voraussetzungen (Reiseanlässe und Verwandtschaftsverhältnisse) beantragt werden. Die Genehmigungen werden kurzfristig erteilt.
[...]
(2. Immediatly the following temporary transitional regulations for travels and constant departures from the GDR to foreign countries take effect:
a) Travel for private purposes to foreign countries can be requested without presence of conditions (Preconditions of travel and family relationships). The permits will be granted short-term.)
https://upload.wikimedia.org/wikipedia/de/d/db/DDR_1989-11-09_Reiseregelungs-Entwurf.pdf
Meaning, that anyone would be allowed to travel outside East Germany (GDR) or rather outside the Warsaw Pact, since people from the GDR already left in droves via the CSSR and Hungary. Hungary officially opened the borders to Austria for GDR citizins on 11. September 1989 after hungarian border troops had already turned a blind eye on GDR refugees for months
https://www.tagesschau.de/multimedia/video/video-24728~_parentId-mauerfallvideos-101.html
and the CSSR allowed GDR citizens to enter the embassy of West Germany (FRG) in Prague, from where they were allowed to leave via train to the FRG after long and hard negotiations between FRG and GDR diplomats
https://www.youtube.com/watch?v=Qh9EwNurawE
From the point, where hungary opened its borders onwards there had been a great fear that the GDR would close its borders completely, even towards Warsaw Pact countries, so this fear was now totally revoked.
Schabowski also read:
[...]
c) Ständige Ausreisen können über alle Grenzübergangsstellen der DDR zur BRD bzw. zu Berlin (West) erfolgen.
[...]
(c) Constant departures can be made on all checkpoints between the GDR and the FRG or Berlin (West) respectively)
This really only related to constant departures, a euphemism for emigration with loss of GDR citizenship, but due to the atmosphere back then (and given the way the new regulations were presented, more on that later) not very much people cared at all, so during the night 9./10. November over time more and more people from both sides of the Iron Curtain moved to the checkpoints and many GDR citizens crossed over to the West without being stopped by the unprepared and confused border guards. This was something the GDR government couldn't turn back.
And here is, where Schabowski really made the mistake:
The Department for Passports and Registration of the GDR Ministry of Interior Affairs had been asked to develop new regulations for costant departure by the Politburo of the GDR, but included also the part with the private travels.
The Politburo had obviously no issue with this when it was presented to them, neither did the Central Comittee, when then Head-of-Party-and-State Egon Krenz read it to them. It only was to not be published until 10. November so that border guards and all to be involved departments and offices could be instructed on the procedures that should take place, but apparently no one told this Schabowski after he had missed the meeting of the Central Committee.
According to Schabowski Krenz even told him to read out the new regulations during the famous press conference at the 9. November, even though it hadn't even passed the Council of Ministers, the cabinet of GDR government. But he didn't do this before he was asked by an italian journalist about it. After some babble on the topic he said that new regulations had been made that would allow every citizen of the GDR to leave the GDR via checkpoints of the GDR ("eine Regelung[...], die es jedem Bürger der DDR möglich macht, äh, über Grenzübergangspunkte der DDR auszureisen"), but he used the german verb "ausreisen" that fits as well for private travels as for constant departures, and he just meant the latter. That might be why none of the 3 other present members of the Central Committee corrected what he said. And after he was asked by a german reporter, when these regulations would take effect he answered „Das tritt nach meiner Kenntnis … ist das sofort, unverzüglich.“ ('This takes for all I know ... it is immediatly, without delay')
Ramifications in the sense that he was persecuted by the GDR justice there were none, not the least because it was a tumultuous time, the government changed at 13. November and the opposition ("Runder Tisch" = 'Round Table') was involved in decisions of the government from 7. December on.
http://revolution89.de/en/revolution/the-battle-for-power/the-round-table-and-the-government/