The Pharo list has some notes about this in March 2011 and Levente was involved.

The issues are no longer accessible, e.g.
https://code.google.com/archive/p/pharo/issues/3342

On 9/20/17, H. Hirzel <hannes.hirzel at gmail.com> wrote:
> Just reposting the message
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2017-September/195308.html
> below so that it gets a proper subject line.
>
>
> Note: SharedQueue and SharedQueue2 are both in the image.
> SharedQueue2 was included into Squeak version 3.9 by MarcusDenker
> (10-07-2005) for further testing.
>
> Lex Spoon notes one year later that no problems have come to light. We
> should start migrating to this. All it requires is replacing
> SharedQueue by SharedQueue2.
>
> Then two years later (12-17-2008)  Keith_Hodges  proposes a migration
> script
>
> "fix begin"
> Installer mantis bug: 1375 fix: 'M1375-SharedQueue2Enable.1.cs'.
> WorldState initialize.
> EventSensor initialize.
> "fix end"
>
> We need somebody to have a look at this script
> 'M1375-SharedQueue2Enable.1.cs' if it is still good to do the task.
>
> BTW Pharo does not have two implementations of SharedQueue.
>
> HH.
>
>
> SharedQueue
> I provide synchronized communication of arbitrary objects between
> Processes. An object is sent by sending the message nextPut: and
> received by sending the message next. If no object has been sent when
> a next message is sent, the Process requesting the object will be
> suspended until one is sent.
>
> SharedQueue2
> An implementation of a shared queue based on class Monitor.  Clients
> may may place items on the queue using nextPut: or remove them using
> methods like next or nextOrNil.  Items are removed in first-in
> first-out (FIFO) order.  It is safe for multiple threads to access the
> same shared queue, which is why this is a "shared" queue.
>
> [monitor] is used to synchronize access from multiple threads.
>
> [items] is an ordered collection holding the items that are in the
> queue.  New items are added  at the end, and old items are removed
> from the beginning.
>
> All methods must hold the monitor while they run.
>
>
>
>
>
>
>
> Levente Uzonyi
> <leves at caesar.elte.hu>	Wed, Sep 20, 2017 at 6:44 PM
> Reply-To: The general-purpose Squeak developers list
> <squeak-dev at lists.squeakfoundation.org>
> To: The general-purpose Squeak developers list
> <squeak-dev at lists.squeakfoundation.org>
> On Wed, 20 Sep 2017, H. Hirzel wrote:
>
>
>     On 9/20/17, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>
>         These methods were there to make it possible to migrate from
> SharedQueue
>         to SharedQueue2 in a live system.
>
>
>     Could you please give some more background information about this
> migration?
>
>
> http://bugs.squeak.org/view.php?id=1375
>
>
>         That migration has not happened yet,
>
>
>     Is there a reason not to do it after 5 years?
>
>
> The mantis issue above has a few potential reasons.
> Another one may be that now there are other potential shared queue
> implementations to replace SharedQueue.
>