Freedom of movement and asylum (often from non eu countries) are seperate issues. What Austria is doing is similar to how we approached the Syrian refugee issue.
Funnily enough issues like this and illegal immigration could be much more difficult to police in future. Our current border checks take place in place, with our border police and customs staff operating there under the Touquet Treaty. That may or not may change post EU. In addition, it's more likely now that Scotland (and possibly Northern Ireland) will quit the union. If Scotland does and eventually joins the EU in its own right, we will then have a land border with an EU country for the first time. The signifiance of that is that there would be nothing stopping hundreds of thousands of immigrants from legally moving to Scotland. They could then of course quite easily illegaly come to England if they wanted to. Something that is much more difficult at present. These are all issues that are worth giving thought to as they could become a reality for us post EU.
I think whatever the case in the future we will have moved away from uncontrolled numbers that could have been half a million a year or more in perpetuity.