Does anyone know if these are the same thing?  The limestone screening is the stuff you use under patio stones,  pathways, etc.
I'm considering experimenting with this as I have heard a mulch of limestone chips is good for potted fig plants...

Nass
The stuff that goes under the patio stone is usually called stone dust. Keep weight consideration in mind if you are going to be moving the pots around in spring and fall. The stone dust is a heavy weight stuff. I may be wrong but if you use it as mulch on top, its heavy weight on top of the light soil may compress the soil faster.
Try it on one pot and see the results.

I will offer this opinion:
Limestone screenings here are the chips and dust that fall thru the screens when crushed limestone is graded.  We can get them at the quarry here, and the materiel ranges from powder-fine dust to chips as large as a dime.  I think that "chips" are screened further to remove the dust, but I cannot swear to that.

Agricultural limestone is very fine; the ag people tell us that the finer the particles the quicker it can be taken up by plants.  This of course is true since the lime must be dissolved by soil acids before it can be used by vegetation. 

Now here is my experience:  I have used dolomitic limestone powder as sold by Walmart, ag lime as sold by agricultural limestone firms who spread it on the land and "screenings" straight from the quarry.  The Walmart dolomite and the ag lime disappear in a season; you cannot find a trace of anything that looks like limestone but the effects are there in the soil.  I'm told by the ag. experts that the effect lasts for about five years.

The "screenings" disappear a bit more slowly.  The dust is gone very quickly but you can find the pebbles, the chips, for some time.  The time depends upon the acidity of the soil  Here on my moderately acid soil I can find larger pebbles for several years, but of course the plants are taking up any lime that dissolves from them.  In a garden I had years back in Tulsa I had mulched with several loads of oak leaves.  I spread a whole pickup truck load of screenings on that 30 by 50 foot garden and the next year I could find no trace of the screenings.  Made a good garden of it. 

My belief is that, if we assume that the lime analysis of the stone and dust are the same, you could spread limestone rock as big as a house and the effects would be no different; the lime would dissolve as fast as soil acids could take it, no more, no less.  If you need it fast, use the dust-fine powder, but screenings will do the job. 
Ox

Thanks Ox, Akram, that is good info.  Totally makes sense...

I am going to experiment with it at some point, but first I need to be eating consistently using the tried and true methods of our community.

I still have issues with a stone dissolving as fast as powder or dust.. Just can't see it happening..I am not expert though my wife still has that job....HAHAHA

This link may answer the question of size

I believe it said about what I said:  the finer the materiel the quicker it is dissolved by soil acids.  Nevertheless, a big rock dissolves over time just as a small one does; it just takes longer. 

Screenings, the mixture of fine dust, sandy granules and little limestone chips will have some portion of its lime available very quickly, some in a year or two and some over several years as the larger chips dissolve.  If you put in a rock as large as a house it may be there for centuries, but it is dissolving all that time.
Ox