If you do thorough enough warmups and count those in the mileage totals, it's pretty tough to get less than 20 mpw unless you do nothing on the weekends.
But I've known 5 sub-1:50 runners who did less than 20 per week for at least December through June. Of course, they were 400/800 types (all sub-47.5 relay legs, the fastest at 45.4). So yeah, it's doable if you've got a good set of wheels to start with and you can figure out how to optimize your training time.
El Caballo is quoted as having run up to 25k (15.6 miles) in a day (in sand) several days per week during base training, but also probably ran 20 miles per week or less for a good portion of the year, at least during the peak of the racing season. Of course, his 44.26 for Montreal gold was the fastest FAT 400 ever run at low altitude at the time, so that's an outrageously good set of wheels.
Most super-elite 800 guys, even the real speed demons, have had some base training. Coe (admittedly an 800/1,500 guy rather than 400/800) cut his mileage down to 30-ish per week at times to focus on the qualities needed for championship racing, but ran 50-70 per week during the off-season for most of his career and got to 100+ near the end of his career in 1986 (this is also when he ran his lifetime best 1,500 time, but whether he had all the tools necessary to have won a major title at that time is anybody's guess). Borzakovskiy also reported doing 110k (68 miles) per week at times.
So don't blow off base training, even if you're coming at the 800 from the 400 side. Give it a chance. It doesn't have to be in the Peter Snell, 100+ per week mode for every runner. Sometimes it's a steadily accumulated lifetime base rather than those big pre-season base periods that will serve you well. But at least get to the point where you can run a good, hard tempo for 20 minutes and kind of feel like a distance runner would - motoring along while feeling strong and on top of the pace instead of struggling and sensing that you have to slow down in the middle. Chances are if you can't work your way up to that within a few years, you won't be able to handle enough high intensity to reach your full potential anyway. A decent amount of high intensity is better than a paltry amount, and 20 mpw of it is pretty much on the paltry side of things if you really want to see how far you can get in this sport.