I don't know of any evidence regarding this training. Though Inspiratoiry Muscle Training with a tresshold training has very good results in track and field athletes.

Not sure about anaerobic conditions. But this recent paper on aerobic performance is quite interesting. 

Lauren, Bryan, et al. "Physiological Change Through Aerobic Exercise Under Hypoxic Conditions With An Elevation Mask." (2015).

I don't really think so, all these altitude masks do is reduce airflow, in my opinion, if they were effective in this matter, would he not just be better off holding his breath? 

Agree with Matt, parcial pressures or involved muscles in inspiration are the issue...but in my opinion if you want the same results (blood) as in altitude you must replicate that kind of conditions. 

A recent study investigated the claims of the Elevation Training Mask to allow for combined respiratory muscle training and altitude exposure during exercise.

"The training mask examined in this study did provide for respiratory muscle training (RMT) and cause hypoxemia when it was worn during endurance exercise. Importantly, the magnitude of hypoxemia was much less than what occurs at terrestrialaltitude, and there was virtually no difference between the two altitude resistance mask configurations that were tested. Reductions in sustained exercise tolerance and maximal exercise capacity would reduce training quality and negatively impact endurance exercise performance. The training mask caused inadequate hyperventilation that led to arterial hypoxemia and psychological discomfort, but the magnitude of these responses were small and they did not vary across mask configurations"

The small changes in arterial hypoxemia will not elicit increases in performance. In another study performed in Military cadets the ETM failed to show a significant effect (p < .05).

In another recent investigation researchers observed the Altitude Training Mask effects in ROTC cadets........."There was no significant effect between groups on fatigue index, anaerobic capacity, peak power, VO2max, or time to exhaustion. These results suggest that the use of the ventilatory training mask during mandatory PT did not elicit superior aerobic or anaerobic adaptations in ROTC cadets"

1)http://www.bioportfolio.com/ …/Functional-respiratory- muscle…

2)http://www.ncbi.nlm.nih.gov/ pubmed/26356482

"Breathing Resistances" are simulated resistances that are "matching or mocking" how hard it would actually be to breathe in (3,000 ft. | 6,000 ft. | 9,000 ft. | 12,000 ft. | 15,000 ft. | 18,000 ft. in "ALTITUDE RESISTANCES".

This study found virtually no difference between the different altitude conditions in thmasks as tested (9k vs 15k) of altitude. 

"There was no difference in V_ O2 among the SHAM, 9K, and 15K conditions (p = 0.210)"  

"As shown, there was no difference in VE/V_ O2 or VE/V_ CO2 between 9K and 15K (p = 0.906 and 0.587; respectively)