I have a wireless Access point with another system using debian and squid/dansguardian as a transparent proxy to filter adult content. I can see that 90% the traffic comes from android phones and people used them to update their applications using wifi instead of using their data plan.
So I tried to force Squid to cache the apk files using those lines on /etc/squid/squid.conf:
acl market rep_mime_type application/vnd.android.package-delta cache allow market
But when check the /var/log/squid/access.log I can not see that Squid is caching
1405755182.383 28048 127.0.0.1 TCP_MISS/200 5858532 GET http://r11---sn-h5q7eney.c.android.clients.google.com/market/GetBinary/GetBinary/com.whatsapp/48513:48450:2? - DIRECT/220.127.116.11 application/vnd.android.package-delta