I didn't use any equipment to measure if the VL2020 is receiving charge when installed on the B1260, however this particular battery has been sitting new and unused in my storage for a few years and during that time it would be pretty much safe to assume that the battery has been discharged due to lack of usage, so as soon as I've installed it and let it recharge for a few hours, powered off and powered back on my A1200, the time was correct, so it would be safe to assume that it is recharging.
In any case, I've spoken to a friend of mine who used to be an Amiga repairman back in the day, and he says that Blizzards most probably have an RTC clock chip on-board which is autosensing the battery type. This could be proven by reading the chip's model # and looking up the specs through Google, but unfortunatelly the chip itself is covered by the battery, and I don't want to desolder it just to be able to read the chip's model number. :-)
Anyway, I guess I'll see how the card behaves in regards to keeping the time correctly for the next few months and in case it completely loses time at some point, I'll assume that the VL2020 is recharging.