If you only need to get from Comp B and C to A, and not between each other, then you would need to NAT on the Company B device, and then encrypt the NAT'd traffic.
access-list BtoA_nat permit ip 192.168.1.0 255.255.255.0 172.16.1.0 255.255.255.0
static (i,o) 192.168.10.0 access-list BtoA_nat
access-list crypto_BtoA permit ip 192.168.10.0 255.255.255.0 172.16.1.0 255.255.255.0
Reference the access-list above in your crypto map.
On site A, your ACL would be:
access-list crypto_AtoB permit ip 172.16.1.0 255.255.255.0 192.168.10.0 255.255.255.0
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