yes, you can... however, you have to be working with a good insurance company (most bands go for cheap) and you have to keep up with exactly what you are carrying in the van. For instance, a policy does not exist where you can just say "i want to cover $10,000 in musical equipment that will also be in the van"... you need to document every guitar, amp, mic, etc.
for instance, in order to cover the equipment in my house i can't just say "i have two $2,000 guitars and three $1,000 microphones and also about $5,000 in other shit". i had to get appraisals, receipts, etc for all of my equipment. and of course, you need to get the police involved right away... hope they do their job correctly... and then hope your insurance company does the same.