Foxford Woollen Mills is a weaving mill, producing fabrics, including the fabric for the Garda Síochána uniform. It does not, to my knowledge, prepare and spin woollen yarn.
The company does not provide much information about the original travel rug (car blanket) presented to Gen. Michael Collins, beyond the fact that they used a 4-ply yarn. This is not particularly helpful, as 4-ply yarn today is a very thin yarn that produces a lightweight fabric unsuited to a travel rug. Presumably, the yarn they used was made up of 4 thick strands, plied together to create a rug yarn, closer to an Aran- or Bulky-weight knitting yarn.
While they do not reveal the source for their weaving yarn for Gen. Collins’ rug, given the period, it is likely that it was sourced from a spinning mill in Ireland, possibly but not necessarily in Co Mayo; and that that spinning mill purchased fleece from Irish sources, possibly but not necessarily locally.
Historically, sheep breeds in Ireland were mixed-use – farmed for wool and meat*. With the exception of a couple of breeds, the wool produced was often of relatively poor quality, too rough for anything but outerwear** or carpeting. There was nonetheless a thriving woollen spinning and weaving industry across Ireland, with mills in many towns, particularly market towns where animal marts took place. In Donegal, there was hardly a settlement of any size without a mill. Virtually everybody had a Donegal tweed suit, purchased as a wedding outfit, worn as Sunday best for decades – often picked apart and re-fashioned according to trends – until they were finally buried in it.
This industry was decimated by the mid-20th century. Petroleum-based yarns destroyed the wool-spinning industry, cheap imports from the far east destroyed the knitwear and weaving industry, trends in agriculture towards specialised farming and a lack of political support for the industry meant that, from the 1960s on, these small local mills disappeared. Today, only 3 of these historic spinning mills survive: Donegal Yarns in Kilcar, Co Donegal; Kerry Woollen Mills in Killarney; and Cushendale Woollen Mills in Graignamanagh, Co Kilkenny. The latter two survived by amalgamating weaving and woollen products into their operation, Donegal Yarns through relationships with weaving mills and with international yarn brands such as Debbie Bliss and Lang Yarns.
Generally, weaving mills did better than spinning mills, partly due to the worldwide cachet of Irish tweed and carpeting, and there are still quite a few like Foxford around. But most sheep in Ireland are meat sheep, there’s no marketing support for shorn wool, so there’s virtually no Irish fleece for the spinning mills, and therefore virtually no Irish-grown yarn for the Irish weaving mills. Almost all the wool dyed and spun in Donegal Yarns comes from Australia, via a cleaning operation in Bradford, England.
And that is why Foxford Mills uses Australian wool: because it exists, and Irish wool (almost***) doesn’t.
*: I’m not aware of milk breeds being of much importance until recently.
**: Aran sweaters, while a 20th-century innovation, were outerwear, worn over a good flannel shirt.
***: There are some small-scale efforts to use Irish fleece – Donegal Yarns is working on a range using Wicklow Cheviot fleece, Cushendale Mills processes Irish Zwartble fleece, and Kerry Woollen Mills adds lowland Galway fleece to imported fleece. There’s also a new mini-mill in Cavan, Olann, which will spin small quantities of fleece (the others only accept commercial quantities in tons) which will likely appeal to hobby and rare-breed farmers with only kilos to process; but this won’t supply a large concern like Foxford Mills.