Regarding lot testing in Canada, shooters can only lot test what's available at the various dealers in Canada. It's reported that Hirsch is the Canadian distributor for Lapua, so presumably all or most Lapua .22LR ammo goes through Hirsch to the dealers. Some dealers may get various .22LR match ammos from sources other than authorized distributors, but there's little public information about that.
How often Canadian dealers get shipments of new Lapua .22LR ammo is not clear. Perhaps it's once or twice annually. Typically there will be a greater number of lots of Center X than Midas + because it is in greater demand. The demand for X-Act, at over $300 per brick, is likely not very high.
It's worth pointing out that the size of a lot can vary. Some lots of CX, for example, can be as small as three cases produced in total. Many lots will have no more than half-a-dozen cases. There are invariably fewer lots made of X-Act than Midas +, and fewer lots of Midas + made than Center X.
The quality of lots can vary as well. Not all lots of X-Act will perform better than Midas +, and not all lots of Midas + will perform better than Center X. It's very possible that the best lots of any variety are identified well before any ammo is sent to distributors around the world. Such identified best lots may only reach Canada by chance.
It's not clear how many different lots of CX, for example, arrive in Canada in any new shipment from the manufacturer. It's doubtful, however, whether more than six or seven different lots of CX are usually delivered to any one dealer at a time. It's likely that in total from a new shipment there must be more lots of CX in Canada at all dealers in total than any one dealer will have in stock.
If dealers don't get large numbers of different lots, but dealers don't get the same lots as others, perhaps shooters may be able to work with more than one dealer to test a larger number of lots than may be available from any one dealer.
Some dealers may on occasion go to the Lapua facilities in Germany to lot test ammo. Any such pre-selected lots identified this way are invariably pre-ordered by their customers and the average buyer will be unlikely to have access to them. No doubt this ammo goes through the distributor. Private individuals will not easily, if at all, be able, to import .22LR ammo directly from the manufacturer.