Yes you can extract the storage of any ITensor or IQTensor. Here is some code analogous to the code linked above but for extracting the storage of a dense, real IQTensor:
auto extractReal = (QDense<Real> const& d)
auto store = applyFunc(extractReal,T.store());
The variable "store" above will now hold a copy of the storage of the IQTensor "T". This storage is an object of type QDense<Real> (or alternatively QDenseReal which is an alias or typedef). I haven't gotten around to documenting the storage types in detail yet, but briefly the definition of QDense is in itensor/itdata/qdense.h and it has two main storage fields: one called "offsets" is a list of block information (the block number, when viewing an IQTensor as a "tensor of tensors" and the offset in the data storage array) and the storage array "store" which is just an array of numbers (real numbers in the case of QDenseReal).