Actually, on the face of it this sounds as if it IS an unlawful tow per VC 22658. As mentioned in 22658(l)(1)(A) the person authorizing the release "shall be present at the time of removal. A phone call is not sufficient. If this were a fire lane or near a fire hydrant, this would be a different matter.
A tenant of a small complex could have initiated the tow, but that does not appear to be the case here.
(l) (1) (A) A towing company shall not remove or commence the
removal of a vehicle from private property without first obtaining
the written authorization from the property owner or lessee,
including an association of a common interest development, or an
employee or agent thereof, who shall be present at the time of
removal and verify the alleged violation, except that presence and
verification is not required if the person authorizing the tow is the
property owner, or the owner's agent who is not a tow operator, of a
residential rental property of 15 or fewer units that does not have
an onsite owner, owner's agent or employee, and the tenant has
verified the violation, requested the tow from that tenant's assigned
parking space, and provided a signed request or electronic mail, or
has called and provides a signed request or electronic mail within 24
hours, to the property owner or owner's agent, which the owner or
agent shall provide to the towing company within 48 hours of
authorizing the tow. The signed request or electronic mail shall
contain the name and address of the tenant, and the date and time the
tenant requested the tow. A towing company shall obtain, within 48
hours of receiving the written authorization to tow, a copy of a
tenant request required pursuant to this subparagraph. For the
purpose of this subparagraph, a person providing the written
authorization who is required to be present on the private property
at the time of the tow does not have to be physically present at the
specified location of where the vehicle to be removed is located on
the private property.
The owner of the property could be charged with an infraction and pay up to $1,000 in fines (and likely more than that in associated assessments and fees).
In general, you'd be correct. However, we generally require the owner of the property also be present to authorize the specific tow. There are exceptions, however.
Predatory tow practices have been so rampant in southern CA that the LAPD has established a unit that addresses nothing but these sorts of tows where companies sign contracts with property owners and then wander about looking for a reason to tow. I believe they count on the hope that vehicle owners won't call them on it ... the law, however, has requirements for signage and authorization that must be met.